Investigation of orthorhombic-to-tetragonal structural phase transition in(Ba1-xCax)(Zr0.05Ti0.95)O3 ferroelectric ceramics using micro-Raman scattering
ABSTRACT 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.
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ABSTRACT: We perform a Raman scattering study to elucidate the mechanism of temperature independent dielectric response of Ba0.767Ca0.233TiO3 (BCTO-0.233) from a viewpoint of phonon dynamics. BCTO-0.233 remains tetragonal below Tc down to 3.5 K. Over-damped soft phonon observed in a pure BaTiO3 is found to become underdamped in BCTO-0.233, suggesting that local dipoles induced by Ca2+ off-centering suppress the hopping of Ti ions to reduce damping of the soft-mode. The temperature dependence of the soft-mode frequency agrees qualitatively with the dielectric permittivity through Lyddane-Sachs-Teller relationship, indicating that the dielectric response of BCTO-0.233 is governed by the soft-mode.Applied Physics Letters 03/2012; 100(10). · 3.52 Impact Factor
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ABSTRACT: The effects of grain size and oxygen vacancies on the dielectric responses of BaTiO3 ceramics were investigated using wideband dielectric spectroscopy. Both dipole and ionic polarizations were enhanced by the reduction in grain size down to 2.5 mum. The annealing in low oxygen partial pressure markedly suppressed the dipole polarization possibly due to the domain-wall clamping by oxygen vacancies. To explain the dielectric response of BaTiO3 ceramics, a complex structure including gradient lattice strain layers (GLSL) were proposed as a model of 90° domain structure.Applied Physics Letters 01/2010; 97. · 3.52 Impact Factor