Electro-caloric effects in the BaTiO 3 -based solid solution ceramics
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ORIGINAL ARTICLE
Electro‑caloric effects in the BaTiO3‑based solid solution ceramics Bit Chan Kim1 · Chae Il Cheon1 Received: 28 February 2020 / Revised: 22 April 2020 / Accepted: 24 April 2020 © The Korean Ceramic Society 2020
Abstract Electro-caloric effect (ECE) was investigated in BaTiO3 (BT)-based solid solution ceramics, Ba(Zr,Ti)O3 (BZT), Ba(Sn,Ti)O3 (BST) and (Ba,Ca)(Zr,Ti)O3 (BCZT) with the composition near an invariant critical point (ICP). The samples were fabricated by the solid-state reaction method and the ECE was obtained by an indirect measurement. The 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples showed the best polarization–electric field (P–E) hysteresis characteristics at room temperature and displayed dielectric peaks at 46, 58, and 66 °C, which are the Curie temperatures. With increasing temperature, the P–E loops changed from typical ferroelectric square shapes to paraelectric slanted shapes in the BT-based solid solution ceramics. The adiabatic temperature change due to the ECE (ΔTECE) showed the maximum values of 0.46 °C at 80 °C, 0.5 °C at 65 °C, and 0.47 °C at 75 °C, respectively, in the 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples. The BT-based solid solution ceramics showed smaller maximum ΔTECE, but broader ΔTECE peaks at nearer room temperature than the BT ceramic. The enhancement of the ECE due to the multi-phase coexistence was not observed in BT-based solid solutions with the compositions near an invariant critical point (ICP) at which several phases coexist. Keywords BaTiO3 · Solid solution · Electro-caloric · Ferroelectric · Ceramics
1 Introduction The environmental-friendly solid-state cooling devices using caloric materials, which generate (or dissipate) heat by applying (or removing) electric, magnetic or mechanical fields, are expected to replace the current cooling devices which use cyclical compression and expansion of the harmful vapors [1–6]. Electro-caloric effect (ECE) is a change in the temperature of a dielectric material upon the application or withdrawal of an electric field under adiabatic conditions [4–6]. ECE has been observed in many ferroelectric, antiferroelectric, and relaxor materials after a discovery in Rochelle Salt in 1930 but did not attract an attention due to a small temperature change up to recently [6]. In 2006, Mischenko et al. reported a giant ECE with an adiabatic temperature change of about 12 K in antiferroelectric PbZr0.95Ti0.05O3 thin films by applying a high electric field of 780 kV/cm [7]. This report inspired a research on the ECE again. In recent years, the ECE in Pb-based bulk ceramics have been * Chae Il Cheon [email protected] 1
Department of Materials Science and Engineering, Hoseo University, Asan 31499, Chungnam, Korea
reported because the cooling performance in thin film materials is limited due to a small mass [8–15]. Due to a global regulation on the toxic materials, the lead-free electrocaloric materials are being investigated [16–30]. BaTiO3 (BT) is a typical lead-free ferroelectric material with a first-order phase
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