Second-Order-Transition Like Characteristic and its Contribution to Strain Temperature Stability in Multiphase Coexistent (K, Na)NbO 3-Based Materials

Abstract

High strain and well temperature stability are contradicted in (K, Na)NbO₃-based (KNN) materials. Herein, well temperature stability with high strain is obtained in multiphase coexistent KNN. Second-order-transition like characteristic contributes to the temperature stability, in which intrinsic lattice structure is the bridge between them. Similar characteristic to second order transition is caused by the reduced discrepancy among different lattice symmetries and broadening temperature region of phase transitions. These integrated factors can slow down the latent heat in first order transition and extend it over a wide temperature region, thereby exhibiting similar characteristic to second order transition. Correspondingly, the abruptly increased strain near the phase transition temperature slows down significantly. In addition, the appearance of pure tetragonal symmetry (P4mm) is deferred to a much higher temperature than T_O-T (temperature of orthorhombic-tetragonal transition), in which strain will inevitably decrease. Thus, well temperature stability with high strain response is realized in multiphase coexistent KNN materials.