Complex electrocaloric behavior and competitive dipole orders in antiferroelectrics

Antiferroelectric (AFE) materials are promising electrocaloric (EC) refrigerants, yet the thermodynamic mechanisms governing their complex positive and negative EC effects remain debated. Here, using a Landau–Kittel phenomenological model, we establish a direct link between competitive dipole orders and EC responses in an AFE system with a ferroelectric (FE)–AFE–paraelectric (PE) phase sequence. By analyzing the temperature evolution of the free-energy landscape, we reveal the stability hierarchy among FE, AFE, and PE orders. The further calculated electric field–temperature phase diagrams reveal that the sign of the EC effect is fundamentally governed by the slope of the phase boundary being traversed, which itself is a manifestation of the underlying entropic and energetic competition. This work transcends phenomenological description to provide a predictive, mechanism-based framework for designing high-performance EC materials via phase-diagram engineering.