Synthesis and dielectric properties development of new thermal stable bismuth pyrochlores

Structure and dielectric properties of pyrochlore solid solutions in the Bi2O3-ZnO-Nb2O5-Sb2O3 (BZNS) system were investigated. The X-ray diffraction technique was used to analyze the phase structure. Also, the atomic valence of Sb in BZNS pyrochlores was confirmed as quinquevalent cation (Sb5+) by X-ray photoelectron spectroscopy. Sb replacing Nb in the series (Bi1.8Zn0.2)(Zn0.6Nb1.4-xSbx)O-7 leads to lower dielectric constant. With increasing amount of Sb5- ions substitution (0 less than or equal to x less than or equal to 1.4), the dielectric constant (epsilon) decreases linearly from 100 to 35 associated with a very low loss (tan delta less than or equal to 4 x 10(-4)). The temperature dependence of dielectric constant varies systematically with x. The ceramics with a temperature coefficient of dielectric constant (alpha(e)) less than +/-15 ppm/degreesC are reported. The data suggest that the B-site cations play an important role in the determination of dielectric properties for the compounds. (C) 2002 Elsevier Science Ltd. All rights reserved.