Low temperature Raman scattering study of barium doped lead ytterbium tantalate ceramics

Raman spectra of a complex perovskite system (Pb1−xBax)(Yb0.5Ta0.5)O3, x = 0.0; 0.1 and 0.2 have been studied at low temperature in the range of 10-250 K. The fascination of the system is that it undergoes a crossover from a highly ordered antiferroelectric (x = 0.0) to ferroelectric (x = 0.1) to disordered relaxor ferroelectric (x = 0.2). The nature of splitting that prevails in F2g (≈60 cm−1), F1g (≈538 cm−1) modes and their gradual merging and disappearance with x indicates an orthorhombic symmetry for x = 0.0 and a pseudo-cubic structure for x = 0.2. The mode at 420 cm−1 suggests the existence of rhombohedral distortion in all the compositions. The soft mode behavior of the F2g modes has been analyzed by fitting the data with the power law ωs = A(TC − T)β.