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

Cubic bismuth zinc niobate pyrochlore (base composition (Bi1.5Zn0.5)(Zn0.5Nb1.5)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 degreesC is 3.0-3.1 eV, indicating low crystallization temperature for the pyrochlore phase. No detectable intermediary phases as BiNbO4 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 degreesC. The phase formation study reveals that a well-crystallized single-phased nanopowder is obtained after calcination at 700 degreesC, indicating that the chemical synthesis conferred a higher chemical homogeneity and reactivity on the powder, modifying the crystallization mechanism. (C) 2004 Elsevier Inc. All rights reserved.