A Giant Electrocaloric Effect in Nanoscale Antiferroelectric and Ferroelectric Phases Coexisting in a Relaxor Pb_0.8Ba_0.2ZrO₃ Thin Film at Room Temperature

Abstract

Recently large electrocaloric effects (ECE) (ΔT = 12 K and ΔS = 8 JK-1 kg-1 at 776 kVcm-1) in antiferroelectric sol-gel PbZr 0.95 Ti 0.05 O 3 thin film and (ΔT = 12.6 K and ΔS = 60 JK-1 kg-1 at 2090 kVcm-1) in ferroelectric polymer P(VDF-TrFE)55/45 thin film were observed near their ferroelectric Curie temperatures 495 K and 353 K, respectively. Here authors demonstrate a giant EC effect (ΔT = 45.3 K and ΔS = 46.9 JK-1 kg-1 at 598 kVcm-1) in relaxor ferroelectric Pb 0.8 Ba 0.2 ZrO 3 (PBZ) thin film fabricated on Pt(111)/TiO x /SiO 2 /Si substrate by a sol-gel method, in which nano-scaled antiferroelectric (AFE) and ferroelectric (FE) phases coexist, at room temperature (290 K) rather than at its Curie temperature (408 K). The giant ECE in such a system is attributed to the coexistence of AFE and FE phases and field-induced nano-scaled AFE to FE phase transition. The giant ECE of PBZ thin film makes it a promising material for the application in cooling systems near room temperature.

Large Electrocaloric Effect in Relaxor Ferroelectric and Antiferroelectric Lanthanum Doped Lead Zirconate Titanate Ceramics

“…Hence this change can be accounted for the increase as the external electric field is lowered. Similar phenomenon of change has been reported by other groups3132. Based on above analyses, it can be concluded that the first ECE peak around 330 K may be attributed to the AFE - FE phase transition induced by the electric field in this temperature range.…”

Electrocaloric effect in PbZrO3 thin films with antiferroelectric-ferroelectric phase competition

“…2(a)). The largest ∆S under the electric field of 500 kV/cm reaches 9 J/kg K, which compares well with the experimental value of 8 J/kg K for PbZr 0.95 Ti 0.05 O 3 films [22] and is within the range of the values reported in the literature [20].…”

Twin‐Peak Electrocaloric Effect in Ferroelectric Phase of Diffusive SrBi1.98La0.02Nb2−xTaxO9 Materials

“…[ 9 ] Positive and negative electrocaloric responses are observed to coexist in x = 1.0 sample well before FE–PE phase transition, Figure 4e. The computed change in values of Δ S and Δ T in Figure 5 shows similarity with the reported work on indirect measurements of pyroelectric coefficient in NBT, PBZ relaxor thin films, [ 1,2 ] Current conclusions on the emergence of positive and negative ECE in SBLNT materials via indirect method perceive dependability from the Maxwell relations those maintain validity in the high temperature range for diffusive ferroelectric materials. Maxwell relations at high temperatures become invalid due to presence of nonergodic relaxor state causing discrepancies between direct and indirect measurements above 343 K (70 °C).…”