In other words, large EC strengths (defined by |Δ T/Δ E| and Δ S/Δ E, where parameters T, S and E are the temperature, isothermal entropy and applied electric field, respectively) are favored. Based on these considerations, a high EC performance material should possess a large isothermal entropy change (Δ S) and hence large adiabatic temperature change (Δ T) under a reasonable electric field ( E). The EC effect of ferroelectric materials has attracted continuous attention because of the potential applications in solid-state refrigeration, which is regarded as the most promising solution for cooling microelectronic devices due to the ease of miniaturization, high efficiency and low cost. The electrocaloric (EC) effect refers to the adiabatic temperature change in a polar material at an electric field, due to the isothermal entropy change associated with the electric-field-induced change in polarization. These greatly enhanced ECEs demonstrate that our simple IAGG method is highly appreciated for synthesizing high-performance electrocaloric materials for efficient cooling devices. A large room-temperature electrocaloric effect (ECE) was observed, with an adiabatic temperature drop (Δ T) of 1.5 K, an isothermal entropy change (Δ S) of 2.48 J The 0.9KNbO 3-0.1BaTiO 3 ceramics exhibit relaxor-like behavior with a diffused phase transition near room temperature, as confirmed by the presence of the polar nanodomain regions revealed through high resolution transmission electron microscope analyses. In this bimodal grain size distribution structure, the extra-large grains (~10–50 μm) were evolved from the micron-sized filler powders, and the fine grains (~0.05–0.35 μm) were derived from the sol precursor matrix. 0.9KNbO 3-0.1BaTiO 3 ceramics, with a bimodal grain size distribution and typical tetragonal perovskite structure at room temperature, were prepared by using an induced abnormal grain growth (IAGG) method at a relatively low sintering temperature.
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