A new type of tungsten bronze ceramic Ba5NdCu1.5Nb8.5O30-delta has been prepared by a conventional solid-state reaction technique. Its structural, dielectric properties were investigated. Rietveld analysis shows that Ba5NdCu1.5Nb8.5O30-delta has a single-phase tetragonal (space group P4bm and lattice constants a = b = 12.4961(4) angstrom, c = 3.9426(8) angstrom, V = 615.66(4) angstrom(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 gamma values are close to 2, confirming the typical relaxor ferroelectric behavior. The disorders of Ba2+ or Nd3+ in A1 sites and Nb5+, Cu2+ in B sites induced by the oxygen vacancies may contribute to this dielectric behavior. (C) 2013 Elsevier Ltd. All rights reserved.