Raman spectroscopy of Na 0.5 Bi 0.5 TiO 3

We have measured the Raman spectra of bismuth sodium titanate in its rhombohedral, tetragonal, and cubic phases, with special attention paid to the phase transitions at 584K and 837K (heating). Both transitions appear to be order-disorder and strongly first order, with large thermal hysteresis. The phonon spectra at temperature slightly below the tetragonal phase are remarkably similar to BaTiO3 with A1(To) modes at 130, 269, and 541 cm−1 (compared with 170, 270, 520 cm−1 in BaTiO3) and an E(TO) at 52 cm−1.