Structure evolution and electric‐field‐induced reversible transition in perovskite Na(Nb1−xTax)O3 ceramics

Abstract

AbstractNa(Nb1−xTax)O3 binary solid‐solution ceramics with high quality were fabricated by conventional solid‐state sintering routes for improving the electric(E)‐field‐induced irreversible polarization and transition behaviors of NaNbO3. The studied results confirm that this binary solid‐solution ceramics exhibit orthorhombic Pbcm space group companying with reduced unit‐cell volume at x ≤ 0.4, and orthorhombic Pbnm space group at x = 0.5. As the Ta5+ content increases in the binary solid‐solutions, the E‐field‐induced irreversible antiferroelectric → ferroelectric (AFE → FE) transition becomes reversible at x ≥ 0.2, giving rise to double‐polarization hysteresis; the key E‐fields triggering both irreversible and reversible transitions (EF) increase in general. In particular, the E‐field‐induced FE phase at x = 0.15 is unstable upon unloading E‐field to zero, which can return to AFE phase with time lapse. At x = 0.5, the Curie temperature (TC) of AFE shifts to below room temperature, but E‐field‐induced reversible transition is still observed, which results in a nonlinear polarization with the lowest hysteresis and contributes to the largest energy‐storage density. This transition is not due to the AFE ↔ FE transition but rather to the order ↔ disorder behavior of polar clusters or/and nanoregions within nonpolar Pbnm structure matrix.