Successive phase transitions–induced multiple boundaries and unprecedented electrocaloric effect in Pb(Yb1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3 system

Abstract Temperature stability of electrocaloric effect (ECE) is a thorny problem in ferroelectrics (FE). A general method is to design ferroelectric‐to‐relaxor phase transition at a sacrifice of electrocaloric (EC) strength. The Pb(Yb 1/2 Nb 1/2 )O 3 antiferroelectrics (AFE) + Pb(Mg 1/3 Nb 2/3 )O 3 relaxors strategy designed in this work is effective to tackle this dilemma [(1 − x )PYN– x PMN, x = 0.08–0.36]. PMN addition induces a successive phase transition and dual phase boundaries of ferrielectric (FIE)‐nonergodic relaxor (NER) and NER‐ergodic relaxor (ER), where ferroelectric polarization/strain and ECE reach a local maximum. Thermally stable Δ T is unexpectedly achieved in FIE ( x = 0.14) and NER ( x = 0.24), except for a generality for ER state ( x = 0.30). A dome‐like variation trend is observed in x = 0.14 and 0.24 with a wide temperature span of ∼60 and ∼55 K (±15%Δ T max ). Notably, x = 0.24 NER possesses a large directly measured Δ T max ∼0.64 K simultaneously. Dielectric/ferroelectric properties clarify that two‐stage transition of AFE rigid‐order de‐texture and dissociation of de‐textured AFE domains into polar nano‐entities accounts for thermal stability of Δ T as the alternation of ordered antipolar domains to disorder relaxors serves as a buffer to compensate for the thermal‐shock enhanced random field. This work not only accounts for the underlying mechanism for thermal stability of Δ T at FIE and NER side for the first time in physics but also provides an exotic approach to seek for high‐performance EC materials in practical applications.