A novel sol-gel route to synthesize (Sr0.5Ba0.5)Nb2O6 ceramics with enhanced electrocaloric effect

Abstract

(Sr0.5Ba0.5)Nb2O6 ultra-fine powders were synthesized by a novel sol-gel route, and the mechanism of the reaction was discussed. SrCO3, BaCO3, oxalate niobium and citric acid were used to initiate the sol-gel process, and ethylene glycol (EG) was added to further polymerize the cross-linking structure. The evolution of the (Sr0.5Ba0.5)Nb2O6 phase, the reaction process and the microstructures were investigated by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy, DSC-TG and scanning electron microscopy. The synthesis temperature of the (Sr0.5Ba0.5)Nb2O6 powders reached as low as 1200°C, and the size and morphology of the powders were controlled by temperature. By adjusting the calcination temperature, we obtained (Sr0.5Ba0.5)Nb2O6 powders with uniform sizes of 20 nm to 500 nm. Then, dense (Sr0.5Ba0.5)Nb2O6 ceramics were successfully prepared using these ultrafine powders. Finally, an enhanced electrocaloric effect (ECE) value of 0.35°C was obtained at 100 kV/cm.