Cation Ordering and Dielectric Properties of PMN-PSN Relaxors

Extended thermal annealing treatments were used to modify the B-site cation order in the (1-x)PMN (x)PSN perovskite system. Extensive 1:1 ordering could be induced in compositions with x ≥ 0.1. The substitution of PSN into PMN produces a large increase in the thermal stability of the 1:1 ordered phase, with the maximum disordering temperature of ~1360°C being observed for x = 0.5. The order-disorder transition temperature for pure PMN was calculated to be 913°C. The changes in stability could be rationalized using the random site model for the cation order. The well ordered, large chemical domain ceramics exhibit relaxor behavior up to x ~ 0.6, for higher values normal ferroelectric behavior was observed. Alterations in the size of the chemical domain size had no significant effect on the properties of the lower x compositions, but induced a transition to relaxor behavior for x > ~ 0.6.