DIELECTRIC AND MICROSTRUCTURE STUDIES OF LEAD MAGNESIUM NIOBATE PREPARED BY PARTIAL OXALATE ROUTE

Lead magnesium niobate (PMN) has been prepared using the partial oxala te method without addition of excess PbO and sintering at four differe nt temperatures, 900, 1000, 1100 and 1200 degrees C. Increase in the s intering temperature resulted in increased dielectric constant which i s attributed to an increase in the grain size. Here we report an usual ly high dielectric constant (24000 at -16 degrees C, 1 kHz) observed i n PMN sintered at 1200 degrees C [PMN (1200)]. The room temperature di electric 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, physic al and dielectric properties and microstructure has been carried out. Grain size appears to be a dominant factor in controlling dielectric c onstant rather than the pyrochlore phase, as claimed earlier.