Synergy of ferroelectric-relaxor transition and multiphase coexistence induced high electrocaloric effect with wide temperature span in Pb0.7Ba0.3ZrO3-based system

In this work, (1-x)Pb0.7Ba0.3ZrO3–xBi(Mg0.5Ti0.5)O3 (PBZ–xBMT) compositions was designed with an integration of ferroelectric–relaxor transition and multiphase coexistence to synergistically optimize electrocaloric effect (ECE) and temperature stability. Rietveld refinements reveal a phase structure change with sequence of R3cH → R3cH + Pm3¯m → Pm3¯m as BMT content increases, whilst relaxation property also increases with downshift in ferroelectric–relaxor transition temperature. Structural evolution is also verified by in-situ Raman spectra and ferroelectric measurements. Interestingly, a large ECE (ΔT ∼ 0.86 K) with a broad temperature span (ΔTspan ∼ 58 K) was successfully obtained in x=0.01 composition, which is believed to be contributed by diffuse phase transition character with multiphase coexistence. This work provides a guideline to exploring ferroelectric materials with high ECE/wide operation span and the reported PBZ–based ceramics with a large ΔT and ΔTspan is a promising candidate in application of solid–state cooling devices.