Continuous Phase Transition Enables Piezoelectric Thermal Stability in KNN‐Based Multilayer Textured Ceramics

ABSTRACT Overcoming the trade‐off between multiphase coexistence and phase transformation in piezoelectrics remains a critical challenge for achieving high and stable piezoelectric performance over a broad temperature range. Here, we resolve this long‐standing dilemma by constructing a continuous phase transition through multilayer ceramic texture engineering. Specifically, two types of (K,Na)NbO ₃ ‐based piezoelectric ceramics with distinct polymorphic phase boundary (PPB) features are physically composed. The composite ceramics exhibit hierarchic phase and domain structures, particularly a continuous phase transition, enabling outstanding piezoelectric performance and thermal stability across a wide temperature range. As a result, the multilayer composite ceramics prepared in this work demonstrate excellent room‐temperature piezoelectric properties, with a piezoelectric coefficient ( d ₃₃ ) ∼ 420 pC N ⁻¹ and an inverse piezoelectric coefficient ( d ₃₃ *) ∼ 600 pm V ⁻¹ . More importantly, within the temperature range of 25°C–100°C, the variation in d ₃₃ and d ₃₃ * values is merely 2%. This work establishes a continuous phase transition‐driven paradigm for enhancing piezoelectric thermal stability, demonstrating universal potential to decouple the constraints imposed by multiphase coexistence and phase transformation in next‐generation piezoelectric materials.