Influence of Cation Order on the Dielectric Properties of Pb(Mg1/3nb2/3)O-3-Pb(Sc1/2nb1/2)O-3 (Pmn-Psn) Relaxor Ferroelectrics

The effect of the B‐site cation chemistry and ordering on the dielectric properties of solid solutions in the (1−x)Pb(Mg1/3Nb2/3)O3–Pb(Sc1/2Nb1/2)O3 (PMN‐PSN) perovskite system was examined in samples with 0.1 ≤x≤ 0.9. Thermal annealing treatments were effective in inducing long‐range B‐site order in the samples within this compositional range. The well‐ordered, large chemical domain ceramics exhibit relaxor behavior up to x=∼0.5; for higher values of x, normal ferroelectric behavior was observed. For x≤ 0.5 reductions in the chemical domain, size had no significant effect on the weak‐field dielectric properties, but induced a transition to relaxor behavior for x > ∼0.6. The disordered PSN‐rich samples undergo a spontaneous zero‐field relaxor to ferroelectric transition similar to that reported previously for PSN. The field‐dependent properties of compositions lying closest to the relaxor to ferroelectric crossover exhibited the highest sensitivity to alterations in the chemical order. The properties of this system are consistent with a “random site” description of the 1:1 ordered Pb(β′1/2β1/2)O3 structure with β′= (Mg(2−2x)/3Nb(1−x)/3Scx) and β″= Nb.