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Materials Research

Print version ISSN 1516-1439On-line version ISSN 1980-5373

Abstract

ZANETTI, Sonia Maria  and  SILVA, Sandra Andréia da. Synthesis and characterization of bismuth zinc niobate pyrochlore nanopowders. Mat. Res. [online]. 2007, vol.10, n.3, pp.261-266. ISSN 1516-1439.  http://dx.doi.org/10.1590/S1516-14392007000300008.

Bismuth zinc niobate pyrochlores Bi1.5ZnNb1.5O7 (a-BZN), and Bi2(Zn1/3Nb2/3)2O 7 (b-BZN) have been synthesized by chemical method based on the polymeric precursors. The pyrochlore phase was investigated by differential scanning calorimetry, infrared spectroscopy, and X ray diffraction. Powder and sintered pellets morphology was examined by scanning electron microscopy. The study of a-BZN phase formation reveals that, at 500 °C, the pyrochlore phase was already present while a single-phased nanopowder was obtained after calcination at 700 °C. The crystallization mechanism of the b-BZN is quite different, occurring through the crystallization of a-BZN and BiNbO4 intermediary phases. Both compositions yielded soft agglomerated powders. a-BZN pellets, sintered at 800 °C for 2 hours, presented a relative density of 97.3% while those of b-BZN, sintered at 900 °C for 2 hours, reached only 91.8%. Dielectric constant and dielectric loss, measured at 1 MHz, were 150 and 4 x/10-4 for a-BZN, and 97 and 8 x 10-4 for b-BZN.

Keywords : Pechini; microwave dielectrics; Bi2O3-ZnO-Nb2O5; powder; chemical method.

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