Bimodal-Structured 0.9KNbO3-0.1BaTiO3 Solid Solutions with Highly Enhanced Electrocaloric Effect at Room Temperature

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. In this bimodal grain size distribution structure, the extra-large grains (similar to 10-50 mu m) were evolved from the micron-sized filler powders, and the fine grains (similar to 0.05-0.35 mu m) were derived from the sol precursor matrix. 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. A large room-temperature electrocaloric effect (ECE) was observed, with an adiabatic temperature drop (Delta T) of 1.5 K, an isothermal entropy change (Delta S) of 2.48 J.kg(-1).K-1 , and high ECE strengths of vertical bar Delta T/Delta E vertical bar = 1.50 x 10(-6) K.m.V-1 and Delta S/Delta E = 2.48 x 10(-6) J.m.kg(-1).K-1.V-1 (directly measured at E = 1.0 MV.m(-1)). These greatly enhanced ECEs demonstrate that our simple IAGG method is highly appreciated for synthesizing high-performance electrocaloric materials for efficient cooling devices.

Automated summary

0.9KNbO(3)-0.1BaTiO(3) ceramics with bimodal grain size distribution and relaxor-like behavior were prepared using an induced abnormal grain growth method, showing a large room-temperature electrocaloric effect.