EFFECT OF RARE EARTH IONS ON THE FERROELECTRIC PROPERTIES OF (Sr(0.6)Ba(0.4))(1-2y)(LiRE)(y)Nb(2)O(6)

Abstract

Crystallographic and dielectric properties of (Sro(0.6)Ba(0.4))(1-2y)(LiRE)(y)Nb(2)O(6) (RE = La, Sm, Dy; 0 <= y <= 0.1) have been investigated with the aim to consider the effect of rare earth elements. For all compositions studied, the transition temperature T(C) increases in succession as the ionic radius of the substituting rare earth ion decreases. With increasing y, both the unit cell volume and axial ratio c/a decrease gradually and the phase transition is significantly broadened. For La modified system, T(C) versus y plot shows a minimum at y = 0.05 while, for Sm and Dy modified systems, T(C) increases quadrically with increasing y. These results are discussed in terms of the relation between T(C) and c/a in the tungsten bronze niobates and combined effect of Li and rare earth ion.