Coexistence of negative and positive electrocaloric effect in lead-free 0.9(K0.5Na0.5)NbO3-0.1SrTiO3 nanocrystalline ceramics

The coexistence of negative and positive electrocaloric effect have been experimentally demonstrated in lead-free 0.9(K0.5Na0.5)NbO3 - 0.1SrTiO(3) nanocrystalline ceramics using an indirect thermodynamic method. The electrocaloric response of - 0.85 K at 276 K and 0.43 K at 330 K were calculated at 40 kV/cm. The corresponding electrocaloric coefficient were estimated to be - 0.24 x 10(-7) K.mV(-1) and 0.7 x 10(-7) K.mV(-1) at 273 K and 333 K, respectively. A large electrical storage energy density 1.46 J/cm(3) were achieved. The results indicate that materials possess a huge potential for electrocaloric refrigeration as a micro-cooler and energy storage capacity for electronic devices. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.