Effects of temperature on the optical and electrical properties of ZnO nanoparticles synthesized by sol–gel method

•ZnO nanoparticles for different thermal treatment temperatures has been synthesized by sol–gel method.•The structural, compositional and morphological properties of the powder were reported.•The size of as-prepared nanoparticles is about 35–54 nm.•The nanoparticles after thermal treatment at 500 °C in air shows a strong luminescence band around 384 nm in the UV range.•The imaginary and real parts of the sample impedance versus frequency, were studied in the range of 40 Hz–2 MHz.

ZnO nanoparticles for different thermal treatment temperatures were prepared by using sol–gel method under supercritical drying of ethyl alcohol. The structural properties showed that the ZnO nanoparticles exhibit hexagonal wurtzite structure. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 40 nm shows a strong luminescence band around 384 nm in the UV range. However, the optical band gap of our samples varied between 3.34 and 3.21 eV with increasing annealing temperature. The imaginary and real parts of the sample impedance versus frequency, were studied in the range of 40 Hz–2 MHz. The Nyquist diagrams were used to identify an equivalent circuit and the fundamental parameters of the circuit. The characteristics of crystallinity, morphology, photoluminescence and electrical conductivity of ZnO nanoparticles were investigated.

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