A chemical route for the synthesis of cubic bismuth zinc niobate pyrochlore nanopowders

Resumo

Cubic bismuth zinc niobate pyrochlore (base composition (Bi 1.5Zn 0.5)(Zn 0.5Nb 1.5)O 7) powders were successfully prepared by a chemical method. The formation mechanism of the pyrochlore phase was investigated by TG-DSC, FT-IR, Raman, and X-ray diffraction (XRD). The optical bandgap for the powders treated at temperatures ranging from 500 to 700°C is 3.0-3.1 eV, indicating low crystallization temperature for the pyrochlore phase. No detectable intermediary phases as BiNbO 4 or a pseudo-orthorhombic pyrochlore were observed at any time and the cubic-BZN phase was already formed after thermal treatment at temperatures as low as 500°C. The phase formation study reveals that a well-crystallized single-phased nanopowder is obtained after calcination at 700°C, indicating that the chemical synthesis conferred a higher chemical homogeneity and reactivity on the powder, modifying the crystallization mechanism. XRD results for cubic-BZN powders treated at 400, 500, 600 and 700°C. Zoomed 2θ range (25-35°) including BiNbO 4 and orthorhombic-BZN powders, also treated at 700°C. © 2004 Elsevier Inc. All rights reserved.

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