The Nature of the Ferroelectric Phase Transition in the Modified SbSI Ceramics

摘要

The modified SbSI (ceramic) has been grown by Bridgman method. The dielectric permi-tivity of modified SbSI along c(z)-axis has been measured using LCR meter as a function of temperature at fixed frequency 1 KHz- The nature of ferroelectric phase transition in the modified SbSI has been discussed using ab initio calculations. Theoretical investigations reveal how ferroelectricity and phase transition in the modified SbSI are closely related to deformation of the unit cell and the phonon interaction. Dielectric measurements reveal that substitution of the individual (I~) with (Cl~) ions creates the deformation of the unit cell and increase the temperature of the ferroelectric phase transition T_C- Deformations of the unit cell change the interaction between phonons and the anharmonicity of soft B_(1u) normal mode.