Dielectric and Raman Spectroscopic Studies of Na0.5 Bi0.5 TiO3- BaSnO3 Ferroelectric System.

A series of lead-free perovskite solid solutions of (1 − x) Na_0.5 Bi_0.5 TiO₃( NBT)- x BaSnO₃( BSN), for 0.0 ≤ x ≤ 0.15 have been synthesized using a high-temperature solid-state reaction route. The phase transition behaviors are studied using dielectric and Raman spectroscopic techniques. The ferroelectric to relaxor phase transition temperature ( T_FR) and the temperature corresponding to maximum dielectric permittivity ( T_m) are estimated from the temperature-dependent dielectric data. Dielectric studies show diffuse phase transition around ~335°C in pure NBT and this transition temperature decreases with increase in x. The disappearance of x-dependence of A₁ mode frequency at ~134 cm⁻¹ for x ≥ 0.1 is consistent with rhombohedral-orthorhombic transition. In situ temperature dependence Raman spectroscopic studies show disappearance and discontinuous changes in the phonon mode frequencies across rhombohedral ( x < 0.1)/orthorhombic ( x ≥ 0.1) to tetragonal transition. [ABSTRACT FROM AUTHOR]