Dielectric and Raman spectroscopy studies of (Na_0.5Bi_0.5)TiO₃ lead-free ceramic

In this study, samples of sodium bismuth titanate (Na_0.5Bi_0.5)TiO₃ (NBT) have been prepared using the solid-state technique. Sintering was done at 1200 °C for 4 h in air atmosphere. X-ray diffraction analysis carried out at room temperature showed the formation of a single-phase compound with a rhombohedral crystal system. Dielectric and Raman spectroscopic characterizations have been performed as a function of temperature. The dielectric study showed the existence of a diffuse phase transition around 330 °C. The Raman spectra was fitted to the individual Raman peaks. The obtained peaks were analyzed by observing the changes in their respective peak positions and intensities with increasing of temperature. At high temperatures, the results showed discontinuous changes in the phonon frequencies across the rhombohedral-tetragonal transition. (author)