Ferroelectric phase transition from orthorhombic-to-tetragonal phase was investigated in (Ba1-xCax)(Zr0.05Ti0.95)O3 ceramics [x=0.05, 0.08, 0.10] by micro-Raman scattering. The room temperature Raman scattering reveals the presence of orthorhombic-tetragonal phase co-existence by emergence of tetragonal phase with increase in calcium content. The temperature dependent Raman spectra also show similar cross-over with hardening of A(TO2) mode and disappearance of A(LO1) mode as system moves from orthorhombic-to-tetragonal phase. A thermal hysteresis of ~10K was observed in orthorhombic-to-tetragonal transition.
[Show abstract][Hide abstract] ABSTRACT: Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O-3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O-3-50(Ba0.7Ca0.3)TiO3 piezoceramics. (c) 2014 AIP Publishing LLC.
[Show abstract][Hide abstract] ABSTRACT: The orthorhombic to tetragonal phase transition in (Ba0.92Ca0.08)(Zr0.05Ti0.95)O3 was investigated using high-temperature X-ray diffraction between 260 and 333 K. The results established the presence of tetragonal (P4mm) and orthorhombic (Amm2) phase co-existence in the temperature range of 293 ≤T≤ 313 K. The tetragonal phase was found to increase from 27% at 293 K to 76% at 313 K. The structural refinement and line-profile analysis ruled out the presence of an intermediate monoclinic structure during P4mmAmm2 crossover. The analysis shows a pure orthorhombic (Amm2) structure for T < 293 K and tetragonal for T > 313 K.
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