Effect of post sinter annealing on the dielectric constants of PMN and PFN

Lead magnesium niobate (PMN) and lead iron niobate (PFN) are the ferroelectric ceramics having perovskite structure. Both of these compounds have high dielectric constant (10 000–20 000) and the change in their dielectric constant with respect to temperature is gradual, showing diffused phase transition peaks at −12°C (PMN) and 110C (PFN) respectively. The dielectric properties of these compounds depend very much on their microstructural features i.e. grain size, grain boundary thickness etc. In this study, the PMN and PFN powders prepared by semi-wet hydroxide route were sintered in PbO atmosphere at 1000–1150°C. The sintered pellets were heated in air at 1000°C for 1/2 to 1 h. Their dielectric properties with respect to temperature were studied and the effect of post sinter annealing on their dielectric constants was analysed.