A giant electrocaloric effect in nanoscale antiferroelectric and ferroelectric phases coexisting in a relaxor Pb_0.8Ba _0.2ZrO₃ thin film at room temperature

Recently, large electrocaloric effects (ECE) in antiferroelectric sol-gel PbZr_0.95Ti_0.05O₃ thin films and in ferroelectric polymer P(VDF-TrFE)55/45 thin films were observed near the ferroelectric Curie temperatures of these materials (495 K and 353 K, respectively). Here a giant ECE (ΔT = 45.3 K and ΔS = 46.9 J K ^-1 kg^-1 at 598 kV cm^-1) is obtained in relaxor ferroelectric Pb_0.8Ba_0.2ZrO₃ (PBZ) thin films fabricated on Pt(111)/TiO_x/SiO₂/Si substrates using a sol-gel method. Nanoscale antiferroelectric (AFE) and ferroelectric (FE) phases coexist at room temperature (290 K) rather than at the Curie temperature (408 K) of the material. The giant ECE in such a system is attributed to the coexistence of AFE and FE phases and a field-induced nanoscale AFE to FE phase transition. The giant ECE of the thin film makes this a promising material for applications in cooling systems near room temperature. A giant electrocaloric effect at room temperature is obtained in coexisting antiferroelectric and ferroelectric phase relaxor Pb_0.8Ba_0.2ZrO₃ thin films. Such an effect is usually obtained only at the Curie temperature. This is therefore a promising material for applications in cooling systems near room temperature.