Effect of calcination temperature on the properties of ZnO nanoparticles

Abstract

ZnO nanoparticles have been synthesized by sol–gel technique using zinc acetate dihydrate and diethanolamine as the precursor materials. The effects of calcination temperatures, i.e., 300, 500, 650, 700, and 750 °C, on the crystallinity, optical properties, and size of fabricated zinc oxide nanoparticles were investigated. X-ray diffraction (XRD) analysis reveals the hexagonal wurtzite structure. Crystallite size estimated by XRD data is about 20 nm and increased by increasing calcination temperature. Particle size was supported by particle size analyzer. Fourier transform infrared spectroscopy was used to classify molecular species through thermal decomposition. Its spectra show the ZnO nanoparticles formation in the wave number range 400–500 cm⁻¹ while bonding was eliminated by heating process. Differential scanning calorimetry–thermal gravimetric analysis/differential thermal analysis curves indicate weight loss by thermal effect. Precursor decomposes at ~250 °C and mass loss took place from 100 to 500 °C. Ultraviolet–visible (UV–Vis) absorption was utilized to analyze the optical properties of samples. It is seen that the band gap value shows only very slight increase with increasing calcination temperature. Best band gap of 3.08 eV was measured for the sample prepared without calcination.