Synthesis and dielectric properties of Ba1-xR2x/3Nb2O6 (R : rare earth) with tetragonal tungsten bronze structure

A series of new compounds, Ba1-xR2x/3Nb2O6 (R = Nd, Eu, Gd, Tb, Dy, Ho and Er ) with tetragonal tungsten bronze (TTB) structure were synthesized For B a-R-Nb-O system, single phase TTB was obtained when X = 0.25. To understand the formation condition of these TTB type compounds, two tolerance factors for TTB, t(A1) and t(A2), were proposed against the coordination polyhedra around Al and A2 site cations, respectively. One of the factors was at lea st a requisition to stabilize crystal structure for all TTB the compounds. Ba1-xR2x/3Nb2O6 showed ferroelectric characteristics and the Curie temperat ure, T-c, increased as, the decrease of the ionic radius of rare earth cati ons. These new compound's have potential to be candidates to apply ferroele ctric random access memory (FRAM). (C) 1999 Elsevier Science Limited. All r ights reserved.