Dielectric Properties and Phase Transitions of Sodium‐Strontium‐Cadmium Niobates

Abstract

Solid solution was observed in the system Na1‐xSrN CdPNbO3 where N + P = x/2 between ≤ x 0.40 when the ratio of N:P was within the limits 1:2 → 2:1. Solid solution was observed at N:P ratios outside these limits but these materials were not studied extensively. A ferroelectric pseudomonoclinic perovskite phase was observed at 25° C when ≤ x & le; 0.10 in the compositional series studied. At higher values of x a ferroelectric pseudotetragonal phase with c/a 1 appeared between the pseudomonoclinic ferroelectric phase and the para‐electric pseudocubic phase which was stable at high temperatures. The pseudotetragonal phase, which exhibited much larger values of €/€0 than the pseudomonoclinic phase, had a large peak in the electrical permittivity when it transformed to the pseudocubic state. The high‐temperature phase observed in these materials became a small‐cell perovskite structure when the subcell edge length attained 3.942 ± 0.002 A as a result of thermal expansion.