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The structural instability of SrTiO3 at T S = 105 K is reinvestigated experimentally and theoretically by birefringence measurements and within the self-consistent phonon approximation. Analogous to BaTiO3 the phase transition shows precursor dynamics starting approximately 60 K above the phase transition temperature. These rotational dynamic clusters compete with precursor effects stemming from the polar soft mode and appear on different length scales as compared to BaTiO3. [ABSTRACT FROM AUTHOR]

The relaxor ferroelectric, Sodium Bismuth Titanate, (Na 0.5 Bi 0.5 TiO 3 ), NBT is an A-site substituted distorted perovskite. An extensive temperature-, pressure- and substitution-dependent study of the crystal structure and phase transitions in this compound has been carried out using neutron/x-ray diffraction techniques. This has been complemented with optical, Raman and computational modelling studies. The temperature-dependent investigation shows that NBT undergoes a first phase transition from the high-temperature cubic prototype (Pm &3macr; m) Phase I to Phase II of tetragonal symmetry (P4bm) and then a second one with strong diffuse character to Phase III of rhombohedral symmetry (R3c). The high-pressure study of NBT has revealed an interesting and unusual relaxor-to-antiferroelectric (R3c → Pnma) phase transition. Structural variations as a function of temperature and doping across the (Na 1-x K x ) 0.5 Bi 0.5 TiO 3 (NKBT) series have also been established. [ABSTRACT FROM AUTHOR]

Details the structural phase transition nomenclature report on phase transition nomenclature. Essential crystallographic and physical characteristics of each phase in the sequence; Eliminating confusion associated with the preset multiple nomenclatures expected to stimulate general use of the proposed nomenclature.