Abstract :
The preparation, microstructure development and dielectric properties of Bi1.5ZnNb1.5O7 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 Bi1.5ZnNb1.5O7 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 (Bi1.5ZnNb1.5O7) 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.
