Investigations on synthesis, characterization and humidity sensing properties of ZnO and ZnO-ZrO2 composite nanoparticles prepared by ultrasonic assisted wet chemical method

•Synthesis of ZnO-ZrO2 composite by ultrasonic assisted wet chemical method.•ZrO2 concentration significantly affects properties of ZnO-ZrO2 composites.•ZrO2 modifies lattice anisotropy and crystallographic orientation of ZnO matrix.•Structural properties affect the humidity sensing performance to a large extent. In the present investigations, Zinc oxide (ZnO) and ZnO-ZrO2 composite nanoparticles were synthesized by ultrasonic assisted wet chemical method to investigate their structural, optical and humidity sensing properties. The synthesized nanoparticles were characterized by the techniques like X ray diffraction (XRD), UV–Vis absorption spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). XRD and EDS were employed to confirm the phase formation and phase purity respectively. SEM micrographs showed that morphology of the parent compound ZnO is considerably changed with varying concentration of ZrO2. The optical absorption spectra showed that optical absorption of ZnO decreases with increase in ZrO2 content in the composite. The observed band gap values for ZnO and ZnO-ZrO2 composites were higher as compared to the bulk sample. The humidity sensing performance was substantiated for all the samples and the result of effect of concentration of ZrO2 in ZnO-ZrO2 composites on sensitivity, response and recovery time are discussed in detail.