*2.1.3 Nanogenerator (NG)*

*Multifunctional Ferroelectric Materials*

exhibit FE properties.

ous engineering fields.

*2.1.2 (s2) PTC thermistor*

*2.1.1 Multilayer capacitor (MLCs)*

made of, nickel (Ni) and copper (Cu) [28].

properties of the materials [16–23].

Resistance (PTCR), sensor, PTC Thermistors, IR detectors, RAM, sonars and in electro optic devices. By doping Barium titanate which is insulator in pure form can be changed into a semiconductor. Barium titanate basically white powder of inorganic compound. With a decrease in temperature the octahedral TiO6 undergoes distortion gives rise to five structural phase transition from hexagonal, cubic, tetragonal, orthorhombic, and rhombohedra. Very large spontaneous polarization and high dielectric constant are observed in this phase due to the distorted octahedral. At Curie point, i.e. above 120°C the distorted octahedral of TiO6 comes to equilibrium result in an isotropic cubic structure [13, 14] so only this phase does not

Capacitor, MLC etc. used first BaTiO3 as the dielectric ceramic with large dielectric constant and dielectric loss for manufacturing. The factor that affects the dielectric properties of the materials is not only its structure but also its synthesis route which will reflect in its size of the grain, density, purity etc. [15]. The Applied frequency of the electric field, temperature and do pants also affects the dielectric

The dielectric constant of Barium titanate prepared by any method increase depends on the grain size and distribution of grains [17, 24]. At room temperature the frequency dependent dielectric constant decreases at low frequency and then increases slightly and become constant at high frequency. Temperature dependent dielectric constant decreases at higher temperature [25]. Ions of different size can be can be added to the perovskite structure. So doping at both A and B site of this perovskite structure is used to tolerate its electrical properties [26]. At A site mono, die and trivalent acceptor do pants are substituted to produce P-type semiconductor, whereas N type semiconductor are obtained by donor dopant of tri, tetra and pentavalent ions at the B site of the perovskite. The concentration of the dopants also affects the electrical properties of Barium titanate. Increase in concentration of Donor dopant makes the semiconducting ceramics to an insulating one. Barium titanate ceramics have application in vari-

Mostly BaTiO3 is used in capacitor due to having a high dielectric constant. In thin dielectric form packed in a minimum space not only with high capacitance but also mechanically tough [27]. It is used as passive component in the circuit for large scale integration (LSI). It is also cost effective one with the use of internal electrode

The high resistivity of BaTiO3 makes it as good candidates for PTC thermistor. Doping at A and B site of BaTiO3 convert them as a semiconducting material. Below the Curie temperature these semiconductor materials have low resistance. Above crystal particle boarder barrier layer persuades by the surface state. So FE characteristics with high dielectric constant exhibit by this crystal boundary of high resistance. So below Curie temperature the potential barrier is small. Low resistivity has been exhibited in these materials due to effortlessly penetration of electron. The height of potential barrier increases above the Curie temperature makes electron difficult to pass through it results in increasing the resistivity of the material. In various electronics circuits this semiconducting BaTiO3 materials are used as constant temperature heaters or switching devices. For temperature or parameter related to temperature can be detected, measured and control of temperature with

**34**

High piezoelectric effect with biocompatibility make them use as Nanogenerator. Piezoelectric potential is induced in between the two electrodes of NG, this is due to mechanical stress. Commercial devices can be work using this generated electrical energy without an external energy source.
