Processing and characterization of microemulsion-derived lead magnesium niobate

Abstract

Lead magnesium niobate, Pb(Mg1/3Nb2/3)O3 (PMN), with 3 wt% excess PbO content has been successfully prepared via a microemulsion processing technique. By stepwise hydrolysis using aqueous ammonia as the precipitant, hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a microemulsion consisting of cyclohexane, mixed poly(oxyethylene)5 nonyl phenol ether (NP5) and poly(oxyethylene)9 nonyl phenol ether (NP9), and an aqueous phase. Upon calcination of the microemulsion-derived precursor at 780 °C, an ultrafine perovskite PMN powder with less than 5% pyrochlore phase was obtained. The percentage of perovskite phase increases with increasing calcination temperature, reaching approximately 98% at 900 °C. The resulting PMN powder exhibits a near-spherical particle morphology although particle agglomerates of approximately 0.3 μm in average diameter occur when they are calcined at 850 °C. When sintered at 1150 °C, the microemulsion-derived PMN showed a maximum relative density of approximately 95.6% theoretical density, which gives a maximum dielectric constant of approximately 11 000 at 1 kHz and a Curie temperature of -6 °C.