An x-ray diffraction and Raman spectroscopy investigation of A-site substituted perovskite compounds: the (Na1-xKx)0.5Bi0.5TiO3(0lexle1) solid solution

Abstract

The (Na_{1 - x} K_x )_0.5 Bi_0.5 TiO₃ perovskite solid solution is investigated using x-ray diffraction (XRD) and Raman spectroscopy in order to follow the structural evolution between the end members Na_0.5 Bi_0.5 TiO₃ (rhombohedral at 300 K) and K_0.5 Bi_0.5 TiO₃ (tetragonal at 300 K). The Raman spectra are analysed with special regard to the hard modes and suggest the existence of nano-sized Bi³⁺ TiO₃ and (Na_{1 - 2x} K_2x )⁺ TiO₃ clusters. The complementary use of XRD and Raman spectroscopy suggests, in contrast to previous reported results, that the rhombohedral tetragonal phase transition goes through an intermediate phase, located at 0.5 x 0.80. The structural character of the intermediate phase is discussed in the light of sub- and super-group relations.