**3.3 Different types of electrochemical cells and their assembly**

There are many examples of construction of electrochemical cells, proposed in the literature (Morachevski et al. 2003).

Electrochemical Cells with the Liquid Electrolyte

in the Study of Semiconductor, Metallic and Oxide Systems 79

microfurnace under vacuum (0.1 Pa) up to 200 ° C for 24 hours. Then the cell was rinsed by purified argon and the electrolyte was poured out at the bottom by turn of the flask. Vacuum-sealed cells can be preserved for a long time and can be used reasonably. This cells

permit to obtain the reproducible results of measurements during many months.

Fig. 5. Cell with control of vacuum and inert gas pression inside.

Fig. 6.Vacuum isothermic cell (firste variant).

We have tested the different types of alloys with three types of cells from 'Pyrex' glass, which had been made by ourselves. One of three cell works well up to 200°C (Vassiliev et al., 1968, 1971) using the salts solution of glicerine as electrolyte. We can also use the same types of cells at the high temperature to 1000°C (Vassiliev et al., 1998a) if we use the refractory material as quartz or alumina glasses. The other two types of cell are operated at high temperatures to softening up 'Pyrex' glass (800-900 K) (Vassiliev et al., 1980, 1993, 1995, 1998b, 2001). When we experiment with a liquid electrolyte, we can use the various electrochemical cells. One of them represents a double H-shaped vessel is suspended on a central tube of 6-8 mm in diameter, fitted with hooks, and which also is served as a cover for the thermocouple. This construction is incorporated inside a protective glass cylinder which is equipped with ground-in cap and two vacuum valves on the sides. This valves permit to control the vacuum and the pression of inert gas inside of the cell. The tungsten current leads with electrodes are soldered in inlet tubes 8 mm in diameter. Height and diameter of the protective cylinder depend on the internal diameter and depth of a using electric furnace. Described construction of the cell is convenient for working with glycerine electrolyte (Pyrex material) and for salt melts (quartz material) (See Fig.5).

Figure 6 shows a scheme of the isothermal Pyrex cell. The lower part of the cell (below the dashed line) is 54 - 60 mm in diameter and about 90 mm in height. The tungsten current leads and the electrodes attached to them are soldered in inlet tubes 8 mm in diameter. The bottom of the cell has cruciblelike holes, which are enable to study both solid and liquid alloys, with no risk of accidental mixing. A calibrated Pt/Pt–10% Rh thermocouple is introduced into the casing, which is soldered in the centre of the cell at the level of the electrodes. Such cells can operate indefinitely between the solidification temperature of the eutectic melt and the onset of softening of Pyrex glass (about 900 K). The offtake of the cell is about 400 mm in length and 25 mm in diameter is fitted with a ground-glass joint. It is served as a container for the electrolyte. The time needed to withdraw the ingot from the storage ampoule, to introduce into the container, and to connect it to the vacuum system does not exceed ten seconds. At the first we pump the cell (10-3 to 10-4 Pa) for a day, then we flush with purified argon, and then the ingot is melted under dynamic vacuum using a portable gas torch. The melt drains down into the lower part of the cell, which is introduced into a microfurnace heated from 50 to 100°C above the melting point of the eutectic mixture. Next, the cell is sealed off at the neck under vacuum and transferred to a preheated working furnace. The electrochemical cell in running order is presented in Fig.7.

The third type of cell (Fig. 8) is a modification of the previous. The bottom of that cell is the same as the previous one. The difference concerns a technic of the electrolyte charging into the cell. For certain systems, such as chacogenides, it is necessary to avoid the vacuum heating of the bottom part of cell that causes an evaporation of volatile metals such as Hg (Vassiliev et al., 1990) or chalcogens (Vassiliev et al., 1980). To put the electrolyte in the vessel we should proceed in this way. An ingot of electrolyte, sealed in a Pyrex ampoule, and a massive porcelain mortar were warmed previously in an oven to 200°C. The ingot was removed gently from the ampoule with a special knife and a Pyrex glass stick as follows. One end of the stick was heated up to temperature of softening with help of the torch. After we have applied this part of stick on the stripe traced with a knife on the ampoule. The ampoule was broken easily and the ingot became free. Then the ingot was grounded into small pieces in a mortar and as soon as possible the pieces were loaded in a small offtake flask and it was connected with cell and vacuum.This flask was heated gradually in a

We have tested the different types of alloys with three types of cells from 'Pyrex' glass, which had been made by ourselves. One of three cell works well up to 200°C (Vassiliev et al., 1968, 1971) using the salts solution of glicerine as electrolyte. We can also use the same types of cells at the high temperature to 1000°C (Vassiliev et al., 1998a) if we use the refractory material as quartz or alumina glasses. The other two types of cell are operated at high temperatures to softening up 'Pyrex' glass (800-900 K) (Vassiliev et al., 1980, 1993, 1995, 1998b, 2001). When we experiment with a liquid electrolyte, we can use the various electrochemical cells. One of them represents a double H-shaped vessel is suspended on a central tube of 6-8 mm in diameter, fitted with hooks, and which also is served as a cover for the thermocouple. This construction is incorporated inside a protective glass cylinder which is equipped with ground-in cap and two vacuum valves on the sides. This valves permit to control the vacuum and the pression of inert gas inside of the cell. The tungsten current leads with electrodes are soldered in inlet tubes 8 mm in diameter. Height and diameter of the protective cylinder depend on the internal diameter and depth of a using electric furnace. Described construction of the cell is convenient for working with glycerine

Figure 6 shows a scheme of the isothermal Pyrex cell. The lower part of the cell (below the dashed line) is 54 - 60 mm in diameter and about 90 mm in height. The tungsten current leads and the electrodes attached to them are soldered in inlet tubes 8 mm in diameter. The bottom of the cell has cruciblelike holes, which are enable to study both solid and liquid alloys, with no risk of accidental mixing. A calibrated Pt/Pt–10% Rh thermocouple is introduced into the casing, which is soldered in the centre of the cell at the level of the electrodes. Such cells can operate indefinitely between the solidification temperature of the eutectic melt and the onset of softening of Pyrex glass (about 900 K). The offtake of the cell is about 400 mm in length and 25 mm in diameter is fitted with a ground-glass joint. It is served as a container for the electrolyte. The time needed to withdraw the ingot from the storage ampoule, to introduce into the container, and to connect it to the vacuum system does not exceed ten seconds. At the first we pump the cell (10-3 to 10-4 Pa) for a day, then we flush with purified argon, and then the ingot is melted under dynamic vacuum using a portable gas torch. The melt drains down into the lower part of the cell, which is introduced into a microfurnace heated from 50 to 100°C above the melting point of the eutectic mixture. Next, the cell is sealed off at the neck under vacuum and transferred to a preheated working

The third type of cell (Fig. 8) is a modification of the previous. The bottom of that cell is the same as the previous one. The difference concerns a technic of the electrolyte charging into the cell. For certain systems, such as chacogenides, it is necessary to avoid the vacuum heating of the bottom part of cell that causes an evaporation of volatile metals such as Hg (Vassiliev et al., 1990) or chalcogens (Vassiliev et al., 1980). To put the electrolyte in the vessel we should proceed in this way. An ingot of electrolyte, sealed in a Pyrex ampoule, and a massive porcelain mortar were warmed previously in an oven to 200°C. The ingot was removed gently from the ampoule with a special knife and a Pyrex glass stick as follows. One end of the stick was heated up to temperature of softening with help of the torch. After we have applied this part of stick on the stripe traced with a knife on the ampoule. The ampoule was broken easily and the ingot became free. Then the ingot was grounded into small pieces in a mortar and as soon as possible the pieces were loaded in a small offtake flask and it was connected with cell and vacuum.This flask was heated gradually in a

electrolyte (Pyrex material) and for salt melts (quartz material) (See Fig.5).

furnace. The electrochemical cell in running order is presented in Fig.7.

microfurnace under vacuum (0.1 Pa) up to 200 ° C for 24 hours. Then the cell was rinsed by purified argon and the electrolyte was poured out at the bottom by turn of the flask. Vacuum-sealed cells can be preserved for a long time and can be used reasonably. This cells permit to obtain the reproducible results of measurements during many months.

Fig. 5. Cell with control of vacuum and inert gas pression inside.

Fig. 6.Vacuum isothermic cell (firste variant).

Electrochemical Cells with the Liquid Electrolyte

we have an average charge of the ion-forming potential:

this case using asbestos must be very pure (Shourov, 1974,1984).

Fig. 9. Scheme of electrochemical cell with diaphragms.

m+

z+

n+

p+

charges of superior ion

charges of lower ion

The solvent is mixture of molten salts ACl+BCl.

in the Study of Semiconductor, Metallic and Oxide Systems 81

The ions of these metals have simultaneously two different charges in the electrolyte. Then

 nA = (mCm + nCn)/(Cm+Cn), (11) where Cm and Cn are the concentrations of ions A with charges m and n in equilibrium with the electrode AxB(1-x). However we can prevent this transfer by separating the electrodes by a diaphragm. Fig. 9 gives an idea of this arrangement. The reference electrodes and electrode comprising of the alloy are studied in the same vessel. These electrodes are separated from each other by the tubes with capillaries that are closed with asbestos plug. In


*m m z m z z*

*Me Me Me Me Me Me*

charges of ions m, z > n, p

*n n p p n p*


*Me Me Me Me Me Me Me Me Me Me solvent solvent solvent solvent*

0 0 1 1 2 1 2 2 0 0 11 1 <sup>2</sup> 12 1 2 2 <sup>2</sup> ( ) ( )

Fig. 7. Electrochemical cell in running order.

Fig. 8.Vacuum isothermic cell (second variant).

#### **3.4 Cell with diaphragm**

In some cases the decrease in activity of metal A does not lead to expected results. This concernes to the metals such as titanium, zirconium, hafnium, uranium, and beryllium ...

Fig. 7. Electrochemical cell in running order.

Fig. 8.Vacuum isothermic cell (second variant).

In some cases the decrease in activity of metal A does not lead to expected results. This concernes to the metals such as titanium, zirconium, hafnium, uranium, and beryllium ...

**3.4 Cell with diaphragm** 

The ions of these metals have simultaneously two different charges in the electrolyte. Then we have an average charge of the ion-forming potential:

$$\mathbf{n}\_{\rm A} = (\mathbf{m}\mathbf{C}'\_{\rm m} + \mathbf{n}\mathbf{C}'\_{\rm n})/(\mathbf{C}'\_{\rm m} + \mathbf{C}'\_{\rm n}),\tag{11}$$

where Cm and Cn are the concentrations of ions A with charges m and n in equilibrium with the electrode AxB(1-x). However we can prevent this transfer by separating the electrodes by a diaphragm. Fig. 9 gives an idea of this arrangement. The reference electrodes and electrode comprising of the alloy are studied in the same vessel. These electrodes are separated from each other by the tubes with capillaries that are closed with asbestos plug. In this case using asbestos must be very pure (Shourov, 1974,1984).


n+ charges of lower ion p+

The solvent is mixture of molten salts ACl+BCl.

Electrochemical Cells with the Liquid Electrolyte

cell sleeve 5- ampule sleeve, 6- to air, 7- to pump.

Fig. 11. Liquid-nitrogen trap.

related details may be changed by the experimenter (Fig.10).

in the Study of Semiconductor, Metallic and Oxide Systems 83

Fig. 10. Simple vacuum post: 1- three-way valve (T=valve), 2- two way valve, 3- gauge, 4-

Vacuum comb permits to accelerate the preparation of alloys (Fig.12). The block-scheme of the EMF measuring is presented in the Fig.13. The configuration of the vacuum post and

M1 is more electronegative than Me2 in a series of electrode potentials.

$$\left[\begin{array}{c} \left[M\!e\_1^{m+}\right]^0\\ \end{array}\right]^0 \,\_{\prime}\left[\begin{array}{c} \left[M\!e\_1^{n+}\right]^0\\ \end{array}\right]^0 \,\_{\prime}\left[\begin{array}{c} \left[M\!e\_2^{n+}\right]^0\\ \end{array}\right]^0 \,\_{\prime}\left[\begin{array}{c} \left[M\!e\_2^{n+}\right]^0\\ \end{array}\right]^0$$


$$\mathbf{E}\_1 = \mathbf{q}\_{\text{all.}} \text{ - } \mathbf{q}\_{\text{Me1}} \text{ / } \mathbf{E}\_2 = \mathbf{q}\_{\text{Me2}} \text{ - } \mathbf{q}\_{\text{all.}}$$

One compare E1 + E2 with E3 (E1 + E2 = E3) to verify the accuracy of the electromotive forces of the chain.
