Abstract
Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN-10PT) ceramic prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The difference is due to the almost two-times-higher breakdown field of the former material, 115 kV/cm, as opposed to 57 kV/cm in the latter. While both ceramic materials have similarly high relative densities and grain sizes (>96%, ≈5 μm) and an almost correct perovskite stoichiometry, the mechanochemical synthesis contributes to a lower level of compositional deviation. The peak permittivity and saturated polarization are slightly higher and the domain structure is finer in the mechanochemically derived ceramic. The secondary phases that result from each synthesis are identified and related to different interactions of the individual materials with the electric field: an intergranular lead-silicate-based phase in the columbite-derived PMN-10PT and MgO inclusions in the mechanochemically derived ceramic.
Highlights
Accepted: 1 April 2021The electrocaloric (EC) effect is a reversible temperature change in a polar material that manifests itself with the application or removal of an electric field
We show that the much higher EC temperature change and breakdown field (BF) of the mechanochemically derived ceramic, compared with those of the columbite-derived PMN-10PT, can be related to microstructural features that are inherently connected to the individual synthesis routes
To understand the reasons for the different responses of the Col and Mech samples to the electric field, we further investigated the concentrations of the contaminants in the PMN-10PT powders due to possible wear of the milling bodies
Summary
Accepted: 1 April 2021The electrocaloric (EC) effect is a reversible temperature change in a polar material that manifests itself with the application or removal of an electric field. It is directly related to the polarization change as a function of temperature and electric field. It is strong in ferroelectric and relaxor materials such as the (1–x)Pb(Mg1/3 Nb2/3 )O3 –xPbTiO3. The PMN-10PT ceramic exhibits a dielectric permittivity maximum at ~45 ◦ C [1]. As the temperature dependence of the EC temperature change (∆TEC ) shows a maximum value in the middle of the low-temperature slope of the dielectric peak [2,3,4], PMN-10PT is an appropriate candidate for EC cooling devices operating in the vicinity of room temperature. PMN-10PT bulk ceramic elements have been used as the active elements of a heat regenerator in a proof-of-concept EC cooling device [5]
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