Negative electrocaloric effect in Ba and Sr-doped PNZST antiferroelectric ceramics

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The electrocaloric effect (ECE) and the phase transition behavior of Ba and/or Sr doped Pb 0.99 Nb 0.02 (Zr 0.85 Sn 0.13 Ti 0.02 ) 0.98 O 3 (PNZST) antiferroelectric ceramics were investigated. The x-ray diffraction (XRD) analysis indicates that introducing Ba causes a phase transition from tetragonal to rhombohedral. The dielectric measurements reveal that with increasing Ba content, the antiferroelectric to ferroelectric phase transition temperature ( T AFE–FE ) decreases rapidly and the ferroelectric to paraelectric transition temperature ( T c ) decreases greatly. However, T AFE–FE increases and T c decreases slightly with addition of Sr. Ba additions can stabilize the FE phase while Sr additions can stabilize the AFE phase. Sr additions decrease the variation of polarization with temperature and increase the phase transition field E AFE–FE . Ba doped PNZST shows a large negative ECE of –2.5 K near room temperature, and Δ T > –2.0 K was obtained in the temperature range from 27 °C to 62 °C.