**8. Applications of ferroelectrics**

Ferroelectric materials have been extensive applications [3, 54] in a large number of areas due to their peculiar and interesting properties such as high permittivity capacitors (BaTiO3), ferroelectric non-volatile FeRAM memories (due to bi-stable polarization in modulation and deflector), pyroelectric sensors, piezoelectric and electrostrictive transducers (TGS crystal), electrooptic and optoelectronic devices (due to their non-linear polarizability), thermistors, storage and laser devices, sensors, resonators and actuators which have revolutionized consumer electronics, automobile industry, biomedical diagnosis, underwater acoustic technology, defense-related sectors, gas sensing devices and surface acoustic wave technology, etc. The major areas of applications [3, 54] of ferroelectrics have received a great deal of attention amongst all the above capacitors, ferroelectric memories, pyroelectric sensors, piezoelectric, electrostrictive transducers, electrooptic devices and thermistors. The basic specifications required for capacitors are small size, large capacitance (materials with a large dielectric constant are desired). High frequency characteristics (ferroelectrics with a high dielectric constant are sometimes associated with dielectric dispersions, which must be taken into account for practical applications). Ferroelectric relaxors such as Pb(Mg1/3Nb2/3)O3 and Pb(Zn1/3Nb2/3) O3 are some examples of these applications.

The bi-stable polarization of ferroelectrics makes them useful for binary memory systems. There are volatile and non-volatile memory devices in erasable semiconductor memories. Non-volatile memory does not require a holding voltage. Dynamic random-access memory (DRAM), which is widely used because of its high integration capability, is an example of volatile memory. Data stored in these

memories are lost when the electric power is shut off. To record information of polarization may be reversed or reoriented by application of an electric field greater than the coercive field. For erasure, the polarization can be returned to its original state with an applied field of opposite polarity. To read the stored information, it is retrieved by electrical or optical means. Optical memory is an electrically addressed light valve. For example, BaTiO3, (Pb,La)(Zr,Ti)O3 and Pb5Ge3O11 single crystals are extensively used as light values. When a ferroelectric thin film with a large polarization-electric field hysteresis is used as the memory capacitor, non-volatile memory is realized. When a voltage is applied to the gate and the field-effect transistor (FET) assumes the "on" state, a pulse voltage to the drain generates a drain current dependent on the remanent polarization state. A large electric field is applied to a ferroelectric film in every process in the ferroelectric RAM (FeRAM), the polarization hysteresis characteristic degrades with increasing cycles. This problem of ferroelectric films needs to be overcome for non-volatile memory applications. The development of the ferroelectric memory started with DRAMs is composed of a FET and memory capacitor, then moved into FeRAMs and is now focused on metal ferroelectric semiconductor field-effect transistors (MFSFETs). BaTiO3, LiNbO3 and KH2PO4 crystals, etc., are some examples of these applications.

The pyroelectric properties of polar materials were studied a long time ago, and such materials were belonged as electric stones, measuring the current or voltage response of a crystal to a temperature change, either by continuous heating or by the absorption of sinusoidally modulated radiation. This is basically due to the temperature dependence of the spontaneous polarization of a polar material. The pyroelectric sensors are widely used for monitoring temperature or infrared radiation (IR). Practical applications of the pyroelectric material in temperature sensors and infrared (IR) light detectors lead to some commercial making of ferroelectric ceramics. Pyroelectric detectors can be used to record infrared images. The converse effect is called the electrocaloric effect, which may be a future cooling system. Materials such as TGS, LiTaO3, Sr1/2Ba1/2Nb2O6 etc. are some examples. Another important application of piezoelectric devices. Certain materials produce electric charges on their surfaces when mechanical stress is applied. The induced charges are proportional to the mechanical stress. This is called the piezoelectric effect, which was discovered in Quartz by Pierre and Jacques Curie in 1880. Materials showing this phenomenon also conversely have a geometric strain proportional to an applied electric field showing the converse piezoelectric effect, discovered by Gabriel Lippmann in 1881. The root of the word "piezo" means "pressure" in Greek. Hence the original meaning of the word piezoelectricity implied "pressure electricity". The phenomenon of Piezoelectricity is widely utilized in the fabrication of various devices such as sensors, transducers, actuators, surface acoustic wave (SAW) devices, frequency control devices etc. Quartz, BaTiO3, (Pb, Sm)TiO3, LiNbO3, and LiTaO3 etc., are some materials that can be used for these applications.

**Author details**

*General Introduction to Ferroelectrics*

*DOI: http://dx.doi.org/10.5772/intechopen.97720*

**27**

Muzaffar Iqbal Khan\* and Trilok Chandra Upadhyay

University), Srinagar (Garhwal), Uttarakhand, India

provided the original work is properly cited.

\*Address all correspondence to: muzaffariqbalkhan786@gmail.com

Department of Physics, Hemvati Nandan Bahuguna Garhwal University (A Central

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

## **Acknowledgements**

Authors are thankful to Prof. S.C. Bhatt, Prof. P.D. Semalty for valuable suggestions and discussions.

*General Introduction to Ferroelectrics DOI: http://dx.doi.org/10.5772/intechopen.97720*

memories are lost when the electric power is shut off. To record information of polarization may be reversed or reoriented by application of an electric field greater than the coercive field. For erasure, the polarization can be returned to its original state with an applied field of opposite polarity. To read the stored information, it is retrieved by electrical or optical means. Optical memory is an electrically addressed light valve. For example, BaTiO3, (Pb,La)(Zr,Ti)O3 and Pb5Ge3O11 single crystals are extensively used as light values. When a ferroelectric thin film with a large polarization-electric field hysteresis is used as the memory capacitor, non-volatile memory is realized. When a voltage is applied to the gate and the field-effect transistor (FET) assumes the "on" state, a pulse voltage to the drain generates a drain current dependent on the remanent polarization state. A large electric field is applied to a ferroelectric film in every process in the ferroelectric RAM (FeRAM), the polarization hysteresis characteristic degrades with increasing cycles. This problem of ferroelectric films needs to be overcome for non-volatile memory applications. The development of the ferroelectric memory started with DRAMs is composed of a FET and memory capacitor, then moved into FeRAMs and is now focused on metal ferroelectric semiconductor field-effect transistors (MFSFETs). BaTiO3, LiNbO3 and KH2PO4 crystals, etc., are some examples of these applications. The pyroelectric properties of polar materials were studied a long time ago, and such materials were belonged as electric stones, measuring the current or voltage response of a crystal to a temperature change, either by continuous heating or by the absorption of sinusoidally modulated radiation. This is basically due to the temperature dependence of the spontaneous polarization of a polar material. The pyroelectric sensors are widely used for monitoring temperature or infrared radiation (IR). Practical applications of the pyroelectric material in temperature sensors and infrared (IR) light detectors lead to some commercial making of ferroelectric ceramics. Pyroelectric detectors can be used to record infrared images. The converse effect is called the electrocaloric effect, which may be a future cooling system. Materials such as TGS, LiTaO3, Sr1/2Ba1/2Nb2O6 etc. are some examples. Another important application of piezoelectric devices. Certain materials produce electric charges on their surfaces when mechanical stress is applied. The induced charges are proportional to the mechanical stress. This is called the piezoelectric effect, which was discovered in Quartz by Pierre and Jacques Curie in 1880. Materials showing this phenomenon also conversely have a geometric strain proportional to an applied electric field showing the converse piezoelectric effect, discovered by Gabriel Lippmann in 1881. The root of the word "piezo" means "pressure" in Greek. Hence the original meaning of the word piezoelectricity implied "pressure electricity". The phenomenon of Piezoelectricity is widely utilized in the fabrication of various devices such as sensors, transducers, actuators, surface acoustic wave (SAW) devices, frequency control devices etc. Quartz, BaTiO3, (Pb, Sm)TiO3, LiNbO3, and LiTaO3 etc., are some materials that can be used for these applications.

*Multifunctional Ferroelectric Materials*

Authors are thankful to Prof. S.C. Bhatt, Prof. P.D. Semalty for valuable

**Acknowledgements**

**26**

suggestions and discussions.
