Structural, electrical, optical and phase investigation of perovskite barium zirconate (BaZrO$_3$) nano-particles prepared through auto-combustion technique

The BaZrO$_3$ ceramics were prepared via sol-gel auto-combustion technique with three Fuel to Oxidant (F/O) ratios ($\varphi$ = 0.5, 1.0 and 1.5) and annealed at 1200$^\circ$C for 2 hours. X-ray diffraction (XRD) and Rietveld refinement data confirmed the cubic perovskite phase with the Pm$\bar3$m (221) space group. These three samples are well indexed in JCPDS no: 06-0399. The ratio F/O = 1.0 gives one a small crystallite size and very high surface area. The ratio F/O = 1.5 provides a very high crystallite size and very low dislocation density. The oxygen vacancies in the samples were analyzed using Raman spectroscopy. The optical band gap energy value increases from 2.02 to 3.09 eV with increasing F/O ratio. Using of impedance spectroscopy for BaZrO$_3$ at room temperature allows us to reveal decreasing Ionic conductivity with an increasing F/O ratio. The Nyquist plot for all samples exhibits a circular arc in the high-frequency zone and nearly a straight line in the low-frequency region. Due to the presence of low grain boundary with high ionic conductivity the BaZrO$_3$ electrolyte material is used for energy storage in devices.