Structure and dielectric properties of Ba5NdCu1.5Nb8.5O30−δ tungsten bronze ceramics

Abstract A new type of tungsten bronze ceramic Ba 5 NdCu 1.5 Nb 8.5 O 30− δ has been prepared by a conventional solid-state reaction technique. Its structural, dielectric properties were investigated. Rietveld analysis shows that Ba 5 NdCu 1.5 Nb 8.5 O 30− δ has a single-phase tetragonal (space group P4bm and lattice constants a  =  b  = 12.4961(4) A, c  = 3.9426(8) A, V  = 615.66(4) A 3 ) tungsten bronze structure. The occupations of sites A and B are quite interesting. A1 sites are fully disordered occupied by Ba ions and Nd ions and A2 sites for Ba ions only, while B-sites are equal for both Cu and Nb ions to occupy. This material exhibits an obvious relaxation behavior in the 213–573 K temperature range. The dielectric constants have been fitted by the modified Curie–Weiss law and all the estimated γ values are close to 2, confirming the typical relaxor ferroelectric behavior. The disorders of Ba 2+ or Nd 3+ in A1 sites and Nb 5+ , Cu 2+ in B sites induced by the oxygen vacancies may contribute to this dielectric behavior.