Impedance spectroscopy, ferroelectric and ferromagnetic properties of 60Bi2O3–10SrO–30Fe2O3 glass-ceramic nano-composites for energy storage applications

Abstract

The glass of composition 60Bi2O3–10SrO–30Fe2O3 (BSFO) (in mol%) was prepared by conventional melt quenching technique. Heat treatment process was applied to the glass samples at temperature close to crystallization temperature (600 °C) for different time intervals of 0, 2, 4 and 8, respectively, to obtain glass ceramic nano-composites. X-ray diffraction (XRD) patterns displayed the formation of a cubic Bi3.43Fe0.57O6 for BSFO glass-ceramic nano-composites. The average nanocrystallite size (D) was determined to be between 13.48 and 17.26 nm. The values of D of the present samples were increased with an increment of heat treatment time. The high resolution-transmission electron microscope (HRTEM) images of a BSFO glass sample that was heat treated at 600 °C for 4 h show the nanocrystallites dispersed in the glass matrix with particle size in the range of 17 nm. The real part of permittivity (ε′) of BSFO decreased sharply with the increment in frequency for all samples. The decrement in the magnitude of the real part of impedance (Z′) with the increment in both frequency and temperature suggests an increase in ac conductivity σac. The correlated barrier hopping (CBH) model can explain the exponent S and temperature behavior we observed throughout all samples. For all glass–ceramic nano-composites, with an increase in the electric field, remnant polarization Pr increases. This confirms its ferroelectric nature. The energy storage density (Wr) is found to be maximum for the HT 8 h sample and equal to 34.3 mJ/cm3. The efficiency (η) of the HT 8 h sample was 65 %. The (M − H) loops of the glass–ceramic nano-composites displayed an antiferromagnetic trend. These observations suggest that the present samples might be a promising option for producing energy storage devices.