A unified phase-field framework for BNT-based pseudo-first-order transition

This is the authors' abstract. We don't add key points for this paper.

We develop a unified phase-field framework that decodes electrocaloric (EC) anomalies at a pseudo-first-order phase transition (PFOPT), addressing a key gap in EC modeling. The framework avoids polarization-scaling artifacts from discrete-field methods and captures transitional EC responses beyond segregated Bi0.5Na0.5TiO3 (BNT)-centered models. The simulations predict an EC temperature change of 14.16 K at a saturation polarization of 0.8 C m−2. A conditional MA-like high-entropy configuration increases the calculated EC entropy change by 28.2% at 0.5 C m−2. The same framework accounts for four PFOPT-related anomalies: subcritical-field release of bound entropy (68.3% of the original bound entropy change upon first release), entropy retention at PFOPT onset (79.5%), asymmetric EC response associated with metastable polarization, and a lower threshold field after linear-dielectric modification. These results provide design criteria for increasing EC entropy change in BNT-based PFOPT systems.