Chemical Engineering Seminar Series: Prof. Pavan Nukala

Proximity induced electrocaloric cooling in ferroelectric hafnia

By exploiting a metal-insulator phase transition (MIT) of Ti4O7 (Ny), we engineer a controlled and reversible polar to non-polar phase transition in thick La-doped hafnia (40 nm). This transition occurs between 125 and 140 K and produces giant negative pyroelectric and electrocaloric effects, which allows us to use these materials for on-chip refrigeration. Refrigeration metrics were estimated between 120 to 200 K, with peak refrigerant capacity of 26.4 JKg-1 (), peak isothermal entropy ΔS~8.15 kJKg-1K-1 () and adiabatic ΔTcooling ~100 K (12 K) at ~140 K and 5 MV/cm (0.5 MV/cm) and are the largest reported in electrocalorics. Our work fundamentally makes a promising suggestion of utilizing proximity effects to induce significant solid-state refrigeration, even at cryogenic temperatures relevant to quantum technologies.