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

Abstract

Raman spectra of a complex perovskite system (Pb 1Àx Ba x Þ(Yb 0:5 Ta 0:5 )O 3 , x ¼ 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 ¼ 0:0) to ferroelectric (x ¼ 0:1) to disordered relaxor ferroelectric (x ¼ 0:2). The nature of splitting that prevails in F 2g (% 60 cm À1 ), F 1g (% 538 cm À1 ) modes and their gradual merging and disappearance with x indicates an orthorhombic symmetry for x ¼ 0:0 and a pseudo-cubic structure for x ¼ 0:2. The mode at 420 cm À1 suggests the existence of rhombohedral distortion in all the compositions. The soft mode behavior of the F 2g modes has been analyzed by fitting the data with the power law ! s ¼ AðT C À TÞ .