Dielectric and microstructure studies of lead magnesium niobate prepared by partial oxalate route

Lead magnesium niobate (PMN) has been prepared using the partial oxalate method without addition of excess PbO and sintering at four different temperatures, 900, 1000, 1100 and 1200 degrees C. Increase in the sintering temperature resulted in increased dielectric constant which is attributed to an increase in the grain size. Here we report an usually high dielectric constant (24000 at -16 degrees C, 1 kHz) observed in PMN sintered at 1200 degrees C [PMN (1200)]. The room temperature dielectric constant and dissipation factor at 1 kHz is similar to 15000 and 0.0025, respectively, for PMN (1200). These values are superior to the reported values. A detailed and systematic study on phase, physical and dielectric properties and microstructure has been carried out. Grain size appears to be a dominant factor in controlling dielectric constant rather than the pyrochlore phase, as claimed earlier.