Coexistence of the Cubic and Tetragonal Phases in Relaxor Ferroelectric SrTiO_3-BiScO_3 System

摘要

Dielectric anomalies specific for relaxor ferroelectrics have been found for the SrTiO_3~--BiScOs system. The relaxor properties of this system are rather unexpected because neither SrTiO_3 nor BiScO_3 are ferroelectrics. An X-ray diffraction analysis revealed that at room temperature the ceramic (1-x)SrTiO_3-xBiScO_3 samples with x = 0.2, 0.3 and 0.4 consist of a mixture of a cubic centrosymmetric Pm3m phase and a tetragonal polar P4mm phase. Lattice parameters for these phases increase as x increases. In addition, it was found by the electron backscattered diffraction method that at room temperature, the fraction of the cubic phase decreases and the fraction of the tetragonal phase increases as the mole fraction of BiScO_3 increases. Phase coexistence is assumed to be one of the reasons for the relaxor properties of the system under study.