Optimizing electrocaloric effect of PbSc _0.5Ta _0.5O ₃ ceramics near/below room temperature by ordering degree modulation

Lead scandium tantalate (PbSc_0.5Ta_0.5O₃, PST) is one of the most promising ferroelectric materials for electrocaloric (EC) refrigeration because of the large enthalpy change (Δ<em>H</em>) 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 (<em>Ω</em>)<em> </em>for PST ceramics in a large scale from 0.51 to 1 by multiple heat treatment processes. For the PST sample with <em>Ω </em>= 1, a large Δ<em>H</em> = 1.06 J g^-1 and a huge EC Δ<em>T</em>_max= 4.26 K (@60 kVcm^-1) are obtained due to the highly ordered arrangement of Sc³⁺ and Ta⁵⁺ ions. With the reduction of <em>Ω</em>, the Curie temperature gradually shifts from RT to below 0 °C, and the phase transition is diffused. A fairly large Δ<em>T</em>_max= 1.57 K is obtained at a rather low temperature of 0 °C in the ceramic with <em>Ω </em>= 0.51. This work proves that lattice ordering is another efficient route to modify ferroelectric features, and the achieved large Δ<em>T</em>_max in a wide temperature range near/below RT facilitates high-performance cooling devices a cascade design towards the most urgent market needs.