Processing and characterization of microemulsion-derived lead magnesium niobate

Lead magnesium niobate, Pb(Mg1/3Nb2/3)O-3 (PMN), with 3 wt% excess PbO cont ent has been successfully prepared via a microemulsion processing technique . By stepwise hydrolysis using aqueous ammonia as the precipitant, hydroxid e precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a microemulsion consisting of cyclohexane, mixed poly(ox yethylene)(5) nonyl phenol ether (NP5) and poly(oxyethylene)(9) nonyl pheno l ether (NP9), and an aqueous phase. Upon calcination of the microemulsion- derived precursor at 780 degrees C, an ultrafine perovskite PMN powder with less than 5% pyrochlore phase was obtained. The percentage of perovskite p hase increases with increasing calcination temperature, reaching similar to 98% at 900 degrees C, The resulting PMN powder exhibits a near-spherical p article morphology although particle agglomerates of similar to 0.3 mu m in average diameter occur when they are calcined at 850 degrees C. When sinte red at 1150 degrees C, the microemulsion-derived PMN showed a maximum relat ive density of similar to 95.6% theoretical density, which gives a maximum dielectric constant of similar to 11 000 at 1 kHz and a Curie temperature o f -6 degrees C.