Dielectric behavior of barium zirconate titanate, Ba(Zr0.15Ti0.85)O-3, relaxor ferroelectric ceramics doped with 0, 0.05, 0.10, and 0.15 mol% Nb2O5 was investigated to elucidate the mechanism of color variation of the ceramics due to both Nb2O5 content and sintering temperature between yellow and blue. The influence of Nb in BZT on dielectric properties has three effects. For small context Nb2O5, 0.05 mol%, the dielectric permittivity of the specimen sintered at 1250 degrees C reaches 7500. The enhancement of dielectric permittivity can be interpreted as the space charge from a double-well potential in NbO6 octahedra. For 0.10 mol%, dielectric permittivity of the blue sample approaches 17,000, dielectric loss is large too, and the relaxor behavior is much more prominent. The result of XPS measurement shows that the binding energy of Ti 2p(3) for blue specimen deceases, which implicates an alteration of Ti4+ -> Ti3+. For 0.15 mol% Nb2O5-doped Ba(Zr1-xTix)O-3, the deep yellow sample one, both dielectric parameters become very small illustrating the forming of a new yellow system BaTiO3-Ba0.5NbO3. (c) 2007 Elsevier B.V. All rights reserved.