Microstructure of PbSc_0·5(Nb, Ta)_0·5O₃: A highly ordered solid solution of complex perovskite compounds

Abstract

Single crystals of a solid solution of the two ferroelectric compounds PbSc_0·5Ta_0·5O₃ and PbSc_0·5Nb_0·5O₃ have been prepared by a flux mixture method, with the chemical formula PbSc_0·5(Nb_0·2Ta_0·3)O₃. The first order ferroelectric-paraelectric phase transition is observed at 44(± 1)°C. X-ray and transmission electron microscopy analyses have shown that this new material exhibits a degree of order greater than 0·9 for the {111} -type ordering with an average size of domains around 60 nm. Moreover, the existence of 110-superstructure reflections is attributed to another atomic distribution on the B site, between Sc^{3 +} and Nb^{5 +}/Ta⁵ cations, with a tetragonal unit cell.