Optimizing electrocaloric effect of PbSc 0.5Ta 0.5O ₃ ceramics near/below room temperature by ordering degree modulation

Lead scandium tantalate (PbSc0.5Ta0.5O₃, PST) is one of the most promising ferroelectric materials for electrocaloric (EC) refrigeration because of the large enthalpy change (ΔH) at room temperature (RT), whose properties are determined by the ordering arrangement of two kinds of heterovalent ions in B-sites. This work continuously adjusts the ordering degree (Ω) for PST ceramics in a large scale from 0.51 to 1 by multiple heat treatment processes. For the PST sample with Ω = 1, a large ΔH = 1.06 J g⁻¹ and a huge EC ΔTmax= 4.26 K (@60 kVcm⁻¹) are obtained due to the highly ordered arrangement of Sc³⁺ and Ta⁵⁺ ions. With the reduction of Ω, the Curie temperature gradually shifts from RT to below 0 °C, and the phase transition is diffused. A fairly large ΔTmax= 1.57 K is obtained at a rather low temperature of 0 °C in the ceramic with Ω = 0.51. This work proves that lattice ordering is another efficient route to modify ferroelectric features, and the achieved large ΔTmax in a wide temperature range near/below RT facilitates high-performance cooling devices a cascade design towards the most urgent market needs.