Bismuth zinc niobate (Bi1.5ZnNb1.5O7) ceramics derived from metallo-organic decomposition precursor solution

The preparation, microstructure development and dielectric properties of Bi_1.5ZnNb_1.5O₇ pyrochlore ceramics by metallo-organic decomposition (MOD) route are reported. Homogeneous precalcined ceramic powders of 13-36 nm crystallite size were obtained at temperatures ranging from 500 to 700 °C. The thermal decomposition/oxidation of the gelled precursor solution was chemically analyzed, TG/DTA, XRD, and SEM, led to the formation of a pure cubic pyrochlore phase with a stoichiometry close to Bi_1.5ZnNb_1.5O₇ which begins to form at 500 °C. The metallo-organic precursor synthesis method, where Bi, Zn and Nb ions are chelated to form metal complexes, allows the control of Bi/Zn/Nb stoichiometric ratio on a molecular scale leading to the rapid formation of bismuth zinc niobate (Bi_1.5ZnNb_1.5O₇) ceramic fine powders with pure pyrochlore structure. The powders were pressed into pellets and can be sintered at temperatures as low as 800-1000 °C. Fine crystalline ceramics with the grain size in the range of 200-500 nm have been obtained at the sintering temperature of 800 °C. The dielectric properties in high frequency to microwave range were measured and discussed.