Perovskite materials are of considerable technological importance, particularly with regard to physical properties such as pyroelectricity and piezoelectricity, dielectric susceptibility, linear and nonlinear optical effects. Many of these properties are coarse-grained effects, which vary enormously from one perovskite to another, and differences in crystal structures are hardly noticeable. The effects of the impending transition are evident in some of the crystal properties at temperatures at least a few degrees away from Tc. The substances BaTiO3 and SrTiO3 have very high permittivity values due to the low frequency of the soft mode. It can be deduced that at room temperature BaTiO3 has numerous advantages over other ferroelectrics such as high mechanical strength, resistance to heat (due to the positive temperature coefficient, PTCR) and humidity, presence of ferroelectric properties with a wide range of temperature (its Curie point is high ≈ 400 K) and ease of production. The presence of abnormally high permittivity in BaTiO3 is linked to the loosening of the crystal lattice of this substance. (The sum of the atomic radii of the 1.96 titanium and oxygen ions is less than the distance between these ions in the 1.99 lattice. The compression of the structure when the Ba atom is replaced by the Sr atom drastically reduces the dielectric constant and the Curie point temperature). Barium-strontium titanate (BaxSr1-xTiO3) is a ferroelectric material in solid solution that has a high dielectric constant and a Curie temperature Tc dependent on the Ba/Sr composition. It is a perovskite-based ferroelectric material and one of the most studied ferroelectric materials, showing normal first-order phase transitions...... middle of paper...... The influence of the electric field on this mode it also influences the interaction of soft modes with other modes in the presence of higher-order anharmonic terms, thus giving the electric field dependence of various properties. The soft mode frequency is held responsible for the dielectric and acoustic anomalies near the phase transition point. It is also evident that the square of the temperature-, defect-, and field-dependent soft mode frequency varies with the defect and electric field parameters in the presence of anharmonicity. The presence of these effects stabilizes the frequency of the soft mode. The temperature-dependent part of the effective frequency of the soft mode is due to a defect. The influence of the defect and electric field on this mode also influences the interaction of the soft mode with other modes, thus giving rise to defect and field dependencies of various dynamical properties .
tags