Selective occupancy of sites by rare earths in K2Nd(1-x)EuxNb5O15 nanopowders, where x = 0, 0. 0025, 0. 025, 0. 05 and 0. 1, prepared by modified polyol method

Abstract

Niobates with tetragonal tungsten bronze TTB-type structure have presented great technological potential due to their dielectric, ferroelectric, pyroelectric properties. The preparation by the modified polyol method and structural characterization of K2Nd(1-x)EuxNb5O15 nanopowders, where x = 0; 0. 0025; 0. 025; 0. 05 e 0. 1, were investigated. The structural parameters were analyzed as a function of concentration of europium ions in the K2NdNb5O15 host structure using the Rietveld method. From structural parameters was determined the TTB-type structure with tetragonal symmetry, where the pentagonal sites is occupied by K+ and Eu3+ ions and tetragonal sites is occupied only by Nd3+ ions. The addition of europium in the host structure led to a decrease in the lattice parameters, compatible with the increasing degree of distortion of NbO6 polyhedra. The average crystallite size showed values between 18. 25 and 26nm.