Influence of Annealing on Microstructure, Electrochemical, and Magnetic Properties of Co-Doped SrTiO3 Nanocubes

Abstract

Effect of annealing on microstructure, electrochemical, and magnetic properties of Co-doped SrTiO3 nanocubes obtained by the hydrothermal method was studied. X-ray diffraction (XRD) results of all as-prepared and annealed Co-doped SrTiO3 samples revealed a cubic perovskite structure with the second phases of SrCO3 and Co3O4in as-prepared and annealed SrTi0.90Co0.10O3 samples, respectively. Agglomerated nanocubes could be clearly observed in all as-prepared and annealed Co-doped samples by scanning electron microscope (SEM) and transmission electron microscope (TEM). X-ray absorption near edge spectroscopy (XANES) results suggested the presence of Co2+ cations in as-prepared Co-doped SrTiO3 samples, while both of Co2+ and Co3+ cations were found in annealed Co-doped SrTiO3 samples. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) results of as-prepared and annealed SrTi1-xCoxO3 (x = 0.05, 0.075 and 0.10) electrodes revealed pseudocapacitor behavior of the Faradaic redox reaction type. The specific capacitance (Csc) was affected by the increase of Co content in all as-prepared and annealed Co-doped SrTiO3 samples with an excellent cycling stability after 200 cycle test of 97.24% and the highest value of 75.28 F g−1 at 1 A g−1 in an annealed SrTi0.925Co0.075O3 electrode. Magnetization measurements at room temperature using vibrating sample magnetometer (VSM) revealed diamagnetic behavior of as-prepared SrTiO3 sample, whereas paramagnetic behavior was observed in all as-prepared Co-doped SrTiO3 samples. After annealing, undoped sample exhibited paramagnetic behavior, whereas ferromagnetic behavior was observed in all Co-doped SrTiO3 samples with the increase of saturation magnetization (Ms) at 10 kOe from 0.58 to 1.63 emu/g and the coercive field (Hc) from 43.71 to 123.87 Oe, suggested to originate from the face-center exchange (FCE) mechanism.