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

Abstract Na(Nb 1− x Ta x )O 3 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 NaNbO 3 . 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 Ta 5+ 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 ( E F ) 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 ( T C ) 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.