**4. Application of new lead-oxifluoride nanoglassceramics for thermal sensors**

The chapter demonstrates application of the new nanoglassceramiсs for luminescent fiber thermal sensors. Also the characteristics of the sensors are compared with traditional ones.

One can see that for the nanoglassceramics the spectrum halfwidth is equal to = 66 nm, while that for the silicate glass it is equal to =20 nm. One has also to note that the new nanoglassceramics reveal the high (>80%) quantum yield of luminescence for the transition

In the Fig.10 are shown the amplification cross-sections for the new nanoglassceramics in comparison with the starting glass (before treatment) and with the commercially available

One can see that the transfer from the starting glass to the nanoglassceramics by heat treatment results in increase of the amplification range from 48 to 64 nm. It is accompanied by the increase of the maximal amplification gain for the same pumping level. For instance, for the starting glass for the pumping level 70% the gain is equal to g=0,35 cm-1, while for the glassceramics it is equal to g=0,42 cm-1. One can also see that the amplification spectrum for the commercial silicate glass is much worsens than that of both of the untreated fluorine-

Let us briefly consider the medium for lasers, emitting at 3 m, which are used first of all in medicine. Today the oxygen-less crystals like LiYF4 or garnet crystals like YAG are used as the matrices for erbium ions. However, it is impossible to fabricate the optical fiber and fiber-optical amplifier on the base of these crystals. Hence the search of new media and realization of fiber-optical lasers, emitting at 3 m, are today a very important task. The new lead-oxyfluoride nanoglassceramics, activated by erbium, can become an interest object

In the Fig.11 is shown the luminescence spectrum of the erbium activated nanoglassceramics

One can see from the Fig.11 that the heat treatment leads to broadening of the luminescence spectrum. It, for instance, makes it possible to tune the laser wavelength within the range 3- 3.15 m. The life time for transition of the *4I11/2→4I13/2* is a very important parameter for lasers operated at 3 m. The life time for new nanoglassceramics achieves 5 ms. In comparison, for crystal of Er:YAG (that very often used as a laser media at 3 m) the life time decay achieves 1 ms. Thus, the new nanoglassceramics is a very attractive candidate

Hence a novel lead-fluoride nanoglassceramics, activated by erbium, reveals the luminescence spectral and laser features, which are not worse than that of the well-known commercial glasses, and exceeds them for such parameters, as the amplification spectrum width and the lifetime of the metastable manifold. At the same time the structure and the content of the nanoglassceramics makes it possible to subject it to a traditional technology the optical fiber production. So one can treat the novel lead-fluoride nanoglassceramics, activated by erbium, is the prospective medium for fiber-optical lasers and amplifiers.

The chapter demonstrates application of the new nanoglassceramiсs for luminescent fiber thermal sensors. Also the characteristics of the sensors are compared with traditional ones.

**4. Application of new lead-oxifluoride nanoglassceramics for** 

containing glass and of the nanoglassceramics on its basis.

from the point of view of realization of a fiber three-micron lasers.

*4I13/2 4I15/2*.

silicate glass.

for the transition *4I11/2 4I13/2*.

for 3 m-fiber lasers.

**thermal sensors** 

Fig. 10. Gain/loss spectra of initial glass (a), glassceramics (b) and commercial silicate glass (c), doped with erbium, for various pumping ratio N2/NEr. Pump wavelength 980 nm.

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 121

requires the precise measurements. In addition, the interferometer quality degrades with

The luminescent sensors are the most prospective ones, because they combine the simple design and high accuracy ( 0,05 K). The majority of such sensors are based upon the

 the temperature re-distribution of the energy across the excited levels, leading to redistribution of radiation intensity in the neighboring luminescence bands with

These effects are observed for the rare earth ions like erbium, neodymium, and dysprosium, and for transient metals like chromium, which are contained in the crystalline or glass-like

The sensors on the base of temperature shift of the luminescence band maximum across spectrum have not very high accuracy of temperature measurement ( 5К), in addition, they have rather large inertia (several seconds). Hence today they are not widely used and were

The advantage of the sensors on the base of temperature redistribution of energy across the excited levels is their high accuracy of temperature measurement up to 0.05К. Such an accuracy is achieved by the use of optical materials with the low phonon (<900 cm-1) spectrum like fluozirconate or telluride glasses. It increases the intensity of radiation of the temperature-tied levels due to the up-conversion filling of the upper excited manifolds and

The disadvantage of such devices is their small temperature range T = 7-500 К. For instance, the fluoride glasses like ZBLAN have a low temperature of softening and melting, while the telluride glasses reveal the high tendency to crystallization with the temperature growth. One can also treat as a disadvantage the high refraction index (n> 2.0), which tantalizes significantly the connection with the standard fused silica fiber (n = 1.47). In addition, these materials have high cost due to the use of the oxygen-less atmosphere (as in the case of the fluoride glasses) or to the toxic nature of raw materials (in the case of telluride glasses),

The advantage of the temperature sensors, based on the variation of the luminescence quenching time with temperature is their small inertia. So one can measure the temperature for the short period of time (several ms) and in the wide spectral range (T = 77-1000 К). The sensors have simple design and low cost. Disadvantage of such sensors is a low accuracy of temperature measurement (> 1 К). Such sensors employ the crystals of YAG:Cr or YAG:Dy as an active medium. The use of crystalline media provides additional complexity to the design, because such sensors are to combine the optical fibers for delivery of the exciting radiation and for collection of the registered signal, and of the active crystal, used as

In such a design the thermally sensitive active crystal is connected with an active crystal by gluing. The length of active crystal is limited by the value of several millimeters, and thus its

the temperature shift of the luminescence band maximum across the spectrum;

time, especially under the high temperature action.

changes in the luminescence quenching with temperature.

following principles:

temperature;

a sensitive element.

replaced by the sensors of other kinds.

thus characterized by high radiative probabilities.

which require some protection measures during the synthesis.

state.

Fig. 11. Luminescence spectrum of the erbium ion in the starting glass and the glassceramics.

In today industry the most widely used (~ 60% of the overall measurements) are the temperature measurements. Wide range of measured temperatures, a big variety of measurement conditions and the requirements to the measuring devices, provide, on one hand, the big variety of the temperature measurement tools, but on the other hand require the development of the novel types of sensors and primary converters, which meet the constantly growing requirements to the accuracy, response and noise protection.

One can separate the big variety of devices for temperature measurement into two big categories – the electrical ones and optical. The optical sensors are used, for instance, for measuring the temperature at the remote object and in the intense electro-magnetic fields. One cannot provide it by means of the electric thermal converters due to high probability of "electric breakdown".

There exist three main types of the optical temperature sensors: the Fabry-Perot optical fiber interferometers; pyrometers – the contact-less sensors, implementing the radiation from the heated body; and the luminescent ones based on luminescence variation during heating.

The use of color pyrometers is limited by the fact that the body, heated to approximately 400 K, is radiating mainly in the mid-IR spectral range. Due to low sensitivity of majority of sensors in this spectral range, data collection is thus tantalized.

The use of fiber-optical interference sensors, based on the Fabry-Perot interferometer, comprised by the fused silica fiber is limited due to a comparatively high cost and to a complicated design, because the shift of the resonant wavelength is relatively small and

**2800 2900 3000 3100 3200 3300**

**Wavelength, nm**

In today industry the most widely used (~ 60% of the overall measurements) are the temperature measurements. Wide range of measured temperatures, a big variety of measurement conditions and the requirements to the measuring devices, provide, on one hand, the big variety of the temperature measurement tools, but on the other hand require the development of the novel types of sensors and primary converters, which meet the

One can separate the big variety of devices for temperature measurement into two big categories – the electrical ones and optical. The optical sensors are used, for instance, for measuring the temperature at the remote object and in the intense electro-magnetic fields. One cannot provide it by means of the electric thermal converters due to high probability of

There exist three main types of the optical temperature sensors: the Fabry-Perot optical fiber interferometers; pyrometers – the contact-less sensors, implementing the radiation from the heated body; and the luminescent ones based on luminescence variation during heating.

The use of color pyrometers is limited by the fact that the body, heated to approximately 400 K, is radiating mainly in the mid-IR spectral range. Due to low sensitivity of majority of

The use of fiber-optical interference sensors, based on the Fabry-Perot interferometer, comprised by the fused silica fiber is limited due to a comparatively high cost and to a complicated design, because the shift of the resonant wavelength is relatively small and

sensors in this spectral range, data collection is thus tantalized.

Fig. 11. Luminescence spectrum of the erbium ion in the starting glass and the

constantly growing requirements to the accuracy, response and noise protection.

**0,0**

**0,2**

**0,4**

**0,6**

**Intensity, a.u.**

glassceramics.

"electric breakdown".

**0,8**

**1,0**

 **Glass**

 **Glassceramics**

requires the precise measurements. In addition, the interferometer quality degrades with time, especially under the high temperature action.

The luminescent sensors are the most prospective ones, because they combine the simple design and high accuracy ( 0,05 K). The majority of such sensors are based upon the following principles:


These effects are observed for the rare earth ions like erbium, neodymium, and dysprosium, and for transient metals like chromium, which are contained in the crystalline or glass-like state.

The sensors on the base of temperature shift of the luminescence band maximum across spectrum have not very high accuracy of temperature measurement ( 5К), in addition, they have rather large inertia (several seconds). Hence today they are not widely used and were replaced by the sensors of other kinds.

The advantage of the sensors on the base of temperature redistribution of energy across the excited levels is their high accuracy of temperature measurement up to 0.05К. Such an accuracy is achieved by the use of optical materials with the low phonon (<900 cm-1) spectrum like fluozirconate or telluride glasses. It increases the intensity of radiation of the temperature-tied levels due to the up-conversion filling of the upper excited manifolds and thus characterized by high radiative probabilities.

The disadvantage of such devices is their small temperature range T = 7-500 К. For instance, the fluoride glasses like ZBLAN have a low temperature of softening and melting, while the telluride glasses reveal the high tendency to crystallization with the temperature growth. One can also treat as a disadvantage the high refraction index (n> 2.0), which tantalizes significantly the connection with the standard fused silica fiber (n = 1.47). In addition, these materials have high cost due to the use of the oxygen-less atmosphere (as in the case of the fluoride glasses) or to the toxic nature of raw materials (in the case of telluride glasses), which require some protection measures during the synthesis.

The advantage of the temperature sensors, based on the variation of the luminescence quenching time with temperature is their small inertia. So one can measure the temperature for the short period of time (several ms) and in the wide spectral range (T = 77-1000 К). The sensors have simple design and low cost. Disadvantage of such sensors is a low accuracy of temperature measurement (> 1 К). Such sensors employ the crystals of YAG:Cr or YAG:Dy as an active medium. The use of crystalline media provides additional complexity to the design, because such sensors are to combine the optical fibers for delivery of the exciting radiation and for collection of the registered signal, and of the active crystal, used as a sensitive element.

In such a design the thermally sensitive active crystal is connected with an active crystal by gluing. The length of active crystal is limited by the value of several millimeters, and thus its

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 123

base of lead-fluoride nanocrystals, containing the rare-earth ions as the active medium for the new generation of the luminescent temperature sensors. In such glassceramics the rareearth ions playing the role of nucleation centers for the crystalline phase, i.e. they are included into the crystal. In addition, the activated glassceramics can be used for the optical fiber production, solving thus the connection problem. It can be solved, for instance, by the way of welding of the activated and nonactivated fibers, improving thus the sensor stability

Change of the temperature results in changing the population of the erbium manifolds 2H11/2 and 4S3/2; in other words, takes place re-distribution of the intensity of luminescence bands with maxima at 522 and 547 nm. So, if the luminescence spectra for definite temperatures are known, one can make a conclusion about the object temperature. The temperature growth results in increase of excitation migrations; as a consequence, the number of the radiation-less transitions is growing and grows the probability of luminescence quenching at admixtures. It explains the gradual decrease of radiation

Fig. 13. Temperature dependence of the luminescence spectrum shape of the erbium-doped

In the Fig.14 is shown the evolution of the luminescence spectrum of the erbium activated specimen of lead-fluoride nanoglassceramics with temperature. The shape of the luminescence spectra is explained by the Stark splitting of the erbium manifolds 4S3/2 (547 nm) and 2H11/2 (522 nm), caused by erbium transfer to the crystalline phase after the secondary heat treatment. If the temperature is increased, the maxima of the peak intensities are shifting one with respect to another, i.e. heating results in thermal redistribution of

excitation between the transitions 4S3/2→4I15/2 and 2H11/2→4I15/2.

nanoglassceramics.

intensity at 547 nm and accompanying it increase of intensity at 522 nm (Fig.13).

to fast changes of temperature and to aggressive environment.

connection with the optical fiber (glued zone) is usually positioned in the zone of high temperature or of the high temperature gradient. This makes an effect onto the sensors reliability during their exploitation under the high temperatures (more than 200oC). It is impossible to replace such a design by a "purely fiber-optical one", containing only of the active crystalline fiber, because the technology of fibers production from the said crystals are yet not developed.

The active medium, which is used in such sensors, is to meet the following requirements: the luminescence has to be excited easily; they are to be easily connected with the fused silica fibers; the radiation is to fill into the spectral range, which is convenient for registration etc.

Erbium ions are often used as the luminescence ion, because they has two thermally tied manifolds *2H11/2* и *4S3/2*. The energy gap between these two manifolds is relatively small, and the temperature growth can redistribute the energy between these levels (see Fig.12). One can excite erbium ions via ytterbium ions, which are the efficient sensitizer, and its absorption bands correspond to the spectral range of high power laser diodes (900-1000 nm).

The environment of the erbium ions strongly influences its luminescence properties, and hence the proper choice of the matrix makes it possible to increase the intensity of luminescence from the levels *2H11/2* and *4S3/2*, which will increase the sensitivity of the sensors on this base.

Fig. 12. The scheme of energy transfer from the Er3+ ion manifolds

The best intensity of luminescence from these levels is provided by erbium ions, placed in the oxygen-free environment – the fluoride, for instance. In such matrices the quantum yield of luminescence s increased, and the efficiency of up-conversion processes is also increased.

One can treat the glassceramics, which contain in their volume the fluoride nanocrystals – like CaF2, PbF2 etc. – as the prospective media for the luminescent temperature sensors. In present paper it has been shown the possibility to use the transparent glassceramics on the

connection with the optical fiber (glued zone) is usually positioned in the zone of high temperature or of the high temperature gradient. This makes an effect onto the sensors reliability during their exploitation under the high temperatures (more than 200oC). It is impossible to replace such a design by a "purely fiber-optical one", containing only of the active crystalline fiber, because the technology of fibers production from the said crystals are

The active medium, which is used in such sensors, is to meet the following requirements: the luminescence has to be excited easily; they are to be easily connected with the fused silica fibers; the radiation is to fill into the spectral range, which is convenient for

Erbium ions are often used as the luminescence ion, because they has two thermally tied manifolds *2H11/2* и *4S3/2*. The energy gap between these two manifolds is relatively small, and the temperature growth can redistribute the energy between these levels (see Fig.12). One can excite erbium ions via ytterbium ions, which are the efficient sensitizer, and its absorption bands correspond to the spectral range of high power laser diodes (900-1000 nm). The environment of the erbium ions strongly influences its luminescence properties, and hence the proper choice of the matrix makes it possible to increase the intensity of luminescence from the levels *2H11/2* and *4S3/2*, which will increase the sensitivity of the

> **2 H9/2 4 F5/2, 4 F3/2 <sup>4</sup> F7/22**

**4 S3/2**

**4 F9/2**

**4 I 11/2**

**4 I 9/2**

**4 I 13/2**

**4 I 15/2**

**H11/2**

Fig. 12. The scheme of energy transfer from the Er3+ ion manifolds

0

5

10

Energy (103 cm-1

)

15

20

Er3+

25

The best intensity of luminescence from these levels is provided by erbium ions, placed in the oxygen-free environment – the fluoride, for instance. In such matrices the quantum yield of luminescence s increased, and the efficiency of up-conversion processes is also increased. One can treat the glassceramics, which contain in their volume the fluoride nanocrystals – like CaF2, PbF2 etc. – as the prospective media for the luminescent temperature sensors. In present paper it has been shown the possibility to use the transparent glassceramics on the

yet not developed.

registration etc.

sensors on this base.

base of lead-fluoride nanocrystals, containing the rare-earth ions as the active medium for the new generation of the luminescent temperature sensors. In such glassceramics the rareearth ions playing the role of nucleation centers for the crystalline phase, i.e. they are included into the crystal. In addition, the activated glassceramics can be used for the optical fiber production, solving thus the connection problem. It can be solved, for instance, by the way of welding of the activated and nonactivated fibers, improving thus the sensor stability to fast changes of temperature and to aggressive environment.

Change of the temperature results in changing the population of the erbium manifolds 2H11/2 and 4S3/2; in other words, takes place re-distribution of the intensity of luminescence bands with maxima at 522 and 547 nm. So, if the luminescence spectra for definite temperatures are known, one can make a conclusion about the object temperature. The temperature growth results in increase of excitation migrations; as a consequence, the number of the radiation-less transitions is growing and grows the probability of luminescence quenching at admixtures. It explains the gradual decrease of radiation intensity at 547 nm and accompanying it increase of intensity at 522 nm (Fig.13).

Fig. 13. Temperature dependence of the luminescence spectrum shape of the erbium-doped nanoglassceramics.

In the Fig.14 is shown the evolution of the luminescence spectrum of the erbium activated specimen of lead-fluoride nanoglassceramics with temperature. The shape of the luminescence spectra is explained by the Stark splitting of the erbium manifolds 4S3/2 (547 nm) and 2H11/2 (522 nm), caused by erbium transfer to the crystalline phase after the secondary heat treatment. If the temperature is increased, the maxima of the peak intensities are shifting one with respect to another, i.e. heating results in thermal redistribution of excitation between the transitions 4S3/2→4I15/2 and 2H11/2→4I15/2.

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 125

sensitive to the temperature changes. One can treat this material as the prospective medium to be used in the fiber-optical luminescent temperature sensors. In comparison with known luminescent sensors the temperature sensor, made from the novel lead-oxyfluoride nanoglassceramics, will have a much shorter response time (tens of milliseconds), higher

0 50 100 150 200 250 300 350 400 450

**Temperature, <sup>0</sup>**

0 50 100 150 200 250 300 350 400 450

Fig. 16. Temperature dependence of ratio of luminescence peaks in the lead-fluoride nanoglassceramics for various erbium ions concentration and for the same duration of

**temperature, C**

}

}

**C**

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1

heat treatment (t = 10 h).

**peak ratio, a.u.**

**Peaks ratio, a. u.**

accuracy (±0.5K) and the rather wide range of measured temperatures (77-1000 K).

 1 2

Fig. 15. Determination of the temperature sensitivity of the material.

 **0,05% mol. 0,2% mol 0,5% mol**

 

Fig. 14. Evolution of green erbium luminescence from the lead-fluoride nanoglassceramics specimen with temperature.

Let us consider problem of temperature sensitivity of the activated material and hence of the temperature sensor. Speaking of the temperature sensitivity we mean the variation of ratio of luminescence peaks at the selected wavelengths for temperature variation in 1 K. The larger is this variation, the larger is the sensitivity. It more evident from the Fig.15: here the specimen 2 is more sensitive to the temperature variation, than the specimen 1, because Δ2> Δ1, i.e. the same temperature variation results in larger variation of the signal.

The increase of erbium ions concentration in glass and in nanoglassceramics leads to growth of the luminescence intensity across the overall observed temperature range (Fig.16). The luminescence intensity also grows up across the overall range of measured temperatures with the increase of the time of heat treatment of the erbium activated lead-fluoride nanoglassceramics (Fig.17).

Hence, varying the volume percentage of the crystalline phase by means of variation the time of heat treatment and also of erbium concentration one can control the curve slope, i.e. to control the temperature sensitivity of glassceramics. The dependencies, which were measured, prevent their exponential character across the overall temperature range, i.e. they are predictable and thus they can be used as a graduation curves for temperature evaluation. Hence the knowledge of ratio of the intensities of two erbium transitions makes it possible to determine the material temperature.

The temperature dependencies for the peak ratio for the starting glass and for the glassceramics are the good evidence that the lead-fluoride nanoglassceramics is the most

**0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0**

**Intensity, a.u**

**Temperature,**

 **C**

Fig. 14. Evolution of green erbium luminescence from the lead-fluoride nanoglassceramics

**500 510 520 530 540 550 560 570 580**

**Wavelength, nm**

Let us consider problem of temperature sensitivity of the activated material and hence of the temperature sensor. Speaking of the temperature sensitivity we mean the variation of ratio of luminescence peaks at the selected wavelengths for temperature variation in 1 K. The larger is this variation, the larger is the sensitivity. It more evident from the Fig.15: here the specimen 2 is more sensitive to the temperature variation, than the specimen 1, because Δ2>

The increase of erbium ions concentration in glass and in nanoglassceramics leads to growth of the luminescence intensity across the overall observed temperature range (Fig.16). The luminescence intensity also grows up across the overall range of measured temperatures with the increase of the time of heat treatment of the erbium activated lead-fluoride

Hence, varying the volume percentage of the crystalline phase by means of variation the time of heat treatment and also of erbium concentration one can control the curve slope, i.e. to control the temperature sensitivity of glassceramics. The dependencies, which were measured, prevent their exponential character across the overall temperature range, i.e. they are predictable and thus they can be used as a graduation curves for temperature evaluation. Hence the knowledge of ratio of the intensities of two erbium transitions makes

The temperature dependencies for the peak ratio for the starting glass and for the glassceramics are the good evidence that the lead-fluoride nanoglassceramics is the most

Δ1, i.e. the same temperature variation results in larger variation of the signal.

specimen with temperature.

nanoglassceramics (Fig.17).

it possible to determine the material temperature.

sensitive to the temperature changes. One can treat this material as the prospective medium to be used in the fiber-optical luminescent temperature sensors. In comparison with known luminescent sensors the temperature sensor, made from the novel lead-oxyfluoride nanoglassceramics, will have a much shorter response time (tens of milliseconds), higher accuracy (±0.5K) and the rather wide range of measured temperatures (77-1000 K).

Fig. 15. Determination of the temperature sensitivity of the material.

Fig. 16. Temperature dependence of ratio of luminescence peaks in the lead-fluoride nanoglassceramics for various erbium ions concentration and for the same duration of heat treatment (t = 10 h).

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 127

3. One can depose three luminophors, emitting red, green and blue light, onto the UV LED surface. Such a LED has a disadvantage – a technology problems with deposition of luminophor layers, as well as luminophor degradation under the UV radiation action. The phosphor-converted LEDs are much cheaper than the RGB LED matrices (per light flow unit) and provide the good white light. Other disadvantages of this type are: (i) the low light efficiency (less than that of RGB matrices) due to light conversion in the luminophor layer; (ii) the problems with homogeneity of luminophores deposition in technology process, and (iii) the degradation of

4. One can use the yellow-green, green and red luminophors, deposited onto the blue LED. As a result, two or three radiations are mixed, providing the white or nearly white light. Today most usually are used InGaN based blue LEDs with luminophor, comprised by the nanopowder of yttrium-aluminum garnet, activated by cerium, emitting in a yellow-green spectral range. The luminophor – the powder of YAG:Ce3+, deposited onto the diode surface, is covered by the protective polymer. The advantages of the polymer medium are the simple technology and the low cost. However, the polymer technology has its own limitation in the case of white LEDs. The polymer has low thermal conductivity, and thus the high-power diodes with the structure "YAG:Ce3+-powder luminophor plus polymer coating" meet the heat sink problems. In addition, the polymers degrade during the long-term thermal and light action.. Hence in the case of high power white LEDs there exists the problem of replacement of the unstable polymer matrices by

The blue LEDs with YAG:Ce3+ powder as luminophor emit the so-called "cold" white light, because their radiation does not cover the overall visible range. This "cold" white light is not always comfortable for eyes, and this is the second disadvantage of such material as luminophor type. One can shift the color temperature range towards the "warm" white light by means of introducing the additional red band into the radiation spectrum. Thus one has to add to the LED of the "cold" white light – InGaN, emitting with the spectral maximum at 450 nm, accompanied by the yellow-green YAG:Ce3+ luminophor with the spectral maximum at 570 nm – some new component, introducing into the spectrum the red component with the maximum at 600-650 nm. The most prospective for this task are, for

one can also obtain various color effects.

luminophors with time.

stronger ones.

green LEDs as well as relatively shorter lifetime of blue diodes. Additional problems arise with technique of mixing the beams, increasing thus the cost of produced LEDs. RGB matrices are widely used in the light-dynamic systems. In addition the large number of LEDs in matrix provides high integral light flow and the high axial light intensity. However, due to the optical system aberrations the light spot has different colors in its center and at the edges. In addition, due to the non-uniform heat sink from the matrix edge and from its center. The LEDs are subjected to different heating. As a result, their color changes due to aging in a different manner and thus the integral color temperature and color are "drifting" during exploitation. Compensation of this unpleasant effect is rather complicated and expensive. The technology of light mixing makes it possible not only to obtain the white light, but also to move across the color diagram by means of changing the current through various LEDs. Special feature of RGB LEDs is the possibility to obtain not only the white light, but also a big variety of light colors with the use of addressing control;

Fig. 17. Temperature dependence of the ratio of erbium luminescence peaks (concentration 0.2 mol %) of the starting glass and of the lead-fluoride nanoglassceramics with the different duration of heat treatment (t = 2, 6, 10 h).

#### **5. Application of new lead-oxifluoride nanoglassceramics for luminophors of LEDs**

The chapter demonstrates application of the new nanoglassceramiсs as a luminophor for light emitted diodes (LED). Also, some characteristics of the luminophor are compared with traditional ones.

Today there exist four main approaches to a white light diodes realization:


 0 hour 2 hour 6 hour 10 hour

0 50 100 150 200 250 300 350 400 450

Fig. 17. Temperature dependence of the ratio of erbium luminescence peaks (concentration 0.2 mol %) of the starting glass and of the lead-fluoride nanoglassceramics with the different

**5. Application of new lead-oxifluoride nanoglassceramics for luminophors** 

Today there exist four main approaches to a white light diodes realization:

The chapter demonstrates application of the new nanoglassceramiсs as a luminophor for light emitted diodes (LED). Also, some characteristics of the luminophor are compared with

1. Fabrication of light emitting diodes (LEDs) on the base of ZnSe semiconductor. The structure comprises the blue ZnSe LEDs, "grown up" on the ZnS substratum. In this case the active region of conductor emits the blue light, while the substratum emits yellow. The white light ZnSe LEDs have some advantages. They are working at the voltage 2.7 V and are very stable with respect to static discharges. They can emit the light for the wide range of color temperatures (3500-8500 K). One can thus fabricate the devices with the "warmer" emission. They also have some disadvantages: they have a short lifetime, high electric resistance and still have not found the wide commercial

2. RGB mixing of colors. Blue, red and green LEDs are positioned tightly on one and the same matrix. Their radiation is mixed by some optical system – for instance, by a lens. As a result a white light is obtained. The main problem in this case is realization of

**Temperature, C**

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1

duration of heat treatment (t = 2, 6, 10 h).

**of LEDs** 

traditional ones.

application.

**Peaks ratio, a. u.**

green LEDs as well as relatively shorter lifetime of blue diodes. Additional problems arise with technique of mixing the beams, increasing thus the cost of produced LEDs. RGB matrices are widely used in the light-dynamic systems. In addition the large number of LEDs in matrix provides high integral light flow and the high axial light intensity. However, due to the optical system aberrations the light spot has different colors in its center and at the edges. In addition, due to the non-uniform heat sink from the matrix edge and from its center. The LEDs are subjected to different heating. As a result, their color changes due to aging in a different manner and thus the integral color temperature and color are "drifting" during exploitation. Compensation of this unpleasant effect is rather complicated and expensive. The technology of light mixing makes it possible not only to obtain the white light, but also to move across the color diagram by means of changing the current through various LEDs. Special feature of RGB LEDs is the possibility to obtain not only the white light, but also a big variety of light colors with the use of addressing control; one can also obtain various color effects.


The blue LEDs with YAG:Ce3+ powder as luminophor emit the so-called "cold" white light, because their radiation does not cover the overall visible range. This "cold" white light is not always comfortable for eyes, and this is the second disadvantage of such material as luminophor type. One can shift the color temperature range towards the "warm" white light by means of introducing the additional red band into the radiation spectrum. Thus one has to add to the LED of the "cold" white light – InGaN, emitting with the spectral maximum at 450 nm, accompanied by the yellow-green YAG:Ce3+ luminophor with the spectral maximum at 570 nm – some new component, introducing into the spectrum the red component with the maximum at 600-650 nm. The most prospective for this task are, for

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 129

of the integral luminescence band maximum to 620 nm. Hence the color temperature is shifting towards higher values (6500 K), i.e. to transfer from the "cold" white light to a

The use of lead oxyfluoride nanoglassceramics, activated by other ions, for instance by terbium ions (green luminescence) and europium ions (red luminescence) makes it possible to use only one luminophore and to prevent the problems, caused by the use of polymer coating and of cerium ions, which have the narrow absorption

The luminescence spectrum now reveals the peaks, produced by luminescence of the Tb3+ ions with the maximum at the wavelength 546 nm (transition 5D47F5) and of the Eu3+ ions with the maximums at 595, 615 and 700 nm (corresponding transitions 5D07F0; 5D07F2; 5D07F4). In a combination with the blue LED without YAG:Ce3+ luminophor these peaks provide the "warm" white light. One has to note specially that the nanoglassceramics, activated by europium and terbium, reveal high thermal and optical strength, and their use as a single luminophor makes it possible to solve the heat sink problems, usual for the high power LEDs. So one can treat the novel oxyfluoride nanoglassceramics, activated by the rare earth ions, as the prospective medium to be used as the luminophor in the high power white

**400 450 500 550 600 650 700 750 800**

**Blue diode +YAG:Ce3+**

Wavelength, nm

Fig. 19. Luminescence of the nanoglassceramics (GC), activated ions of Tb3+ and Eu3+ and of

the YAG:Ce3+ powder, excited by the commercial blue diode.

**Blue Diode+Tb3+**

 **and Eu3+**

"warm" one.

bands (Fig.19).

light LEDs.

**0,0**

**0,2**

**0,4**

**0,6**

Intensity, a.u.

**0,8**

**1,0**

instance, the materials with the europium ion admixture. However, this type of LEDs has a significant disadvantage – the rather narrow bands of absorption by cerium ions in the nanocrystals of the yttrium-aluminum garnet. In the case of mass production there exists the variation of the luminescence band maximum due to the technology reasons. In this case is possible only partial overlapping or even mismatch of the bands of LED emission and cerium absorption, providing the significant influence onto the white LED emission intensity.

One can use this problem by use of other luminophor activators – for instance, terbium ions with the emission band maximum at 550 nm and ions of three-valence europium, which introduces into the blue LED emission the red component. As a result, the mixing of blue, green and red light takes place; such an approach is similar to RGB technology.

In present work we have tried to solve the mentioned problems by means of the novel leadoxyfluoride nanoglassceramics, activated europium and terbium.

In the Fig.18 are shown the luminescence spectra of the lead-oxyfluoride nanoglassceramics, activated by three valence europium ions with various concentration under the excitation by the commercial blue LED with the additional YAG:Ce3+ luminophor. In this case the nanoglassceramics plays the role of the additional luminophor.

Fig. 18. Luminescence of Ce3+ in YAG powder and joint luminescence of Eu3+ ions with different concentrations in the glassceramics (GC) and of Ce3+ ions in YAG powder under excitation by the commercial blue diode.

The use of europium ions results in arises of the additional bands in the red spectral range. As a result there is observed the wide integral band of Ce3+ and Eu3+ luminescence with the maximum at ~580 nm. The increase of Eu3+ concentration leads to additional shift

instance, the materials with the europium ion admixture. However, this type of LEDs has a significant disadvantage – the rather narrow bands of absorption by cerium ions in the nanocrystals of the yttrium-aluminum garnet. In the case of mass production there exists the variation of the luminescence band maximum due to the technology reasons. In this case is possible only partial overlapping or even mismatch of the bands of LED emission and cerium absorption, providing the significant influence onto the white LED emission

One can use this problem by use of other luminophor activators – for instance, terbium ions with the emission band maximum at 550 nm and ions of three-valence europium, which introduces into the blue LED emission the red component. As a result, the mixing of blue,

In present work we have tried to solve the mentioned problems by means of the novel lead-

In the Fig.18 are shown the luminescence spectra of the lead-oxyfluoride nanoglassceramics, activated by three valence europium ions with various concentration under the excitation by the commercial blue LED with the additional YAG:Ce3+ luminophor. In this case the

**400 450 500 550 600 650 700 750 800**

Wavelength, nm

**Blue diode + YAG:Ce3+ + GC:EuF3 (1%)** **Blue diode + YAG:Ce3+ + GC:EuF3 (3%)**

**Blue diode+ YAG:Ce3+**

Fig. 18. Luminescence of Ce3+ in YAG powder and joint luminescence of Eu3+ ions with different concentrations in the glassceramics (GC) and of Ce3+ ions in YAG powder under

The use of europium ions results in arises of the additional bands in the red spectral range. As a result there is observed the wide integral band of Ce3+ and Eu3+ luminescence with the maximum at ~580 nm. The increase of Eu3+ concentration leads to additional shift

green and red light takes place; such an approach is similar to RGB technology.

oxyfluoride nanoglassceramics, activated europium and terbium.

nanoglassceramics plays the role of the additional luminophor.

**0,0**

excitation by the commercial blue diode.

**0,2**

**0,4**

**0,6**

Intensity, a.u.

**0,8**

**1,0**

intensity.

of the integral luminescence band maximum to 620 nm. Hence the color temperature is shifting towards higher values (6500 K), i.e. to transfer from the "cold" white light to a "warm" one.

The use of lead oxyfluoride nanoglassceramics, activated by other ions, for instance by terbium ions (green luminescence) and europium ions (red luminescence) makes it possible to use only one luminophore and to prevent the problems, caused by the use of polymer coating and of cerium ions, which have the narrow absorption bands (Fig.19).

The luminescence spectrum now reveals the peaks, produced by luminescence of the Tb3+ ions with the maximum at the wavelength 546 nm (transition 5D47F5) and of the Eu3+ ions with the maximums at 595, 615 and 700 nm (corresponding transitions 5D07F0; 5D07F2; 5D07F4). In a combination with the blue LED without YAG:Ce3+ luminophor these peaks provide the "warm" white light. One has to note specially that the nanoglassceramics, activated by europium and terbium, reveal high thermal and optical strength, and their use as a single luminophor makes it possible to solve the heat sink problems, usual for the high power LEDs. So one can treat the novel oxyfluoride nanoglassceramics, activated by the rare earth ions, as the prospective medium to be used as the luminophor in the high power white light LEDs.

Fig. 19. Luminescence of the nanoglassceramics (GC), activated ions of Tb3+ and Eu3+ and of the YAG:Ce3+ powder, excited by the commercial blue diode.

New Nanoglassceramics Doped with Rare Earth Ions and Their Photonic Applications 131

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### **6. Conclusion**

Today the novel optical materials are determining the progress in photonics. In this paper it has been shown that one of prospective directions in the field of optical material science for photonics is the development of the nanostructurized glassceramic materials. One example of realization of a novel optical material - the transparent lead-oxyfluoride nanoglassceramics, doped with the rare-earth ions - has been presented. It was shown that due to spontaneous crystallization in a glass are growing the new crystalline phases – the yttrium-oxyfluoride of lead, the lanthanide oxyfluoride of lead and yttriumlanthanide oxyfluoride of lead. The size of crystalline phase is 15-40 nm, providing thus transparency of nanoglassceramics in a visible and near-IR spectral ranges and thus putting it into the class of optical materials. One can also treat the novel optical nanoglassceramics as a multi-functional material, because it can be used in various fields of photonics. Several examples of the novel material applications in photonics have been demonstrated. Moreover, the features of the novel material with the known analogs have been compared. For instance, it was shown that the novel material can compete with traditional materials in production of fiber-optical lasers and amplifiers, working at 1.5 and 3 m. It was shown that the novel material can be successfully used for the temperature sensors, including fiber-optical ones. It has been also demonstrated that the novel material can be successfully used as a luminophor for white light LEDs.

#### **7. References**


Today the novel optical materials are determining the progress in photonics. In this paper it has been shown that one of prospective directions in the field of optical material science for photonics is the development of the nanostructurized glassceramic materials. One example of realization of a novel optical material - the transparent lead-oxyfluoride nanoglassceramics, doped with the rare-earth ions - has been presented. It was shown that due to spontaneous crystallization in a glass are growing the new crystalline phases – the yttrium-oxyfluoride of lead, the lanthanide oxyfluoride of lead and yttriumlanthanide oxyfluoride of lead. The size of crystalline phase is 15-40 nm, providing thus transparency of nanoglassceramics in a visible and near-IR spectral ranges and thus putting it into the class of optical materials. One can also treat the novel optical nanoglassceramics as a multi-functional material, because it can be used in various fields of photonics. Several examples of the novel material applications in photonics have been demonstrated. Moreover, the features of the novel material with the known analogs have been compared. For instance, it was shown that the novel material can compete with traditional materials in production of fiber-optical lasers and amplifiers, working at 1.5 and 3 m. It was shown that the novel material can be successfully used for the temperature sensors, including fiber-optical ones. It has been also demonstrated that the novel material can be successfully used as a luminophor

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**6. Conclusion** 

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**7. References** 


**6** 

*Russia* 

**Fianite in Photonics** 

*A. M. Prokhorov General Physics Institute, Russian Academy of Sciences* 

The further progress in photonics, as well as in many other technological fields is connected with application of new materials. Fianite is the material of such kind. Fianites are single crystals of zirconia- or hafnia-based cubic solid solutions with yttrium, calcium, magnesium or lanthanides (from gadolinium to lutetium) stabilizing oxides (ZrO2 (HfO2)·R2O3, where R - Y, Gd … Lu). Industrial technology of synthesis of fianite has been for the first time developed in Russia in the Lebedev Physical Institute of the Russian Academy of Sciences (FIAN in Russian), as has entitled crystals[1, 2]. Serial production of the crystals has been already started in the early seventies of XX century [3-5]. Currently, fianite crystals are in the second position by the volume of worldwide production following silicon. Fianite single crystals – zirconia-based solid solutions (or "yttrium stabilized zirconia" - YSZ) are widely

Fig. 1. Great color variety of the crystals combined with unique optical properties makes fianite single crystals a promising material for jewellery, arts and Crafts (left); fianite

Recently, in the countries with the developed microelectronics a significant growth of interest to various aspects of fianite application in semiconductor technologies has been observed. Fianite is an extremely promising multipurpose material for new optoelectronics technologies due to its unique combination of physical and chemical properties. It can be used in virtually all of the main technological stages of the production of micro-, opto- and SHF-electronics: as a bulk dielectric substrate, a material for buffer layers in heteroepitaxy; a material for insulating, antireflection, and protective layers in the devices and as a gate

**1. Introduction** 

known worldwide as jewelry material (fig. 1).

substrates 3" in diameter (right).

dielectric [6-22].

Alexander Buzynin

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