Optimization of molar concentrations for enhanced crystallinity and bandgap tuning of ZrO2 thin films via spray pyrolysis for advanced optical applications

In this study, Zirconium oxide (ZrO2) thin films were synthesized on glass substrates at 400°C using the Spray Pyrolysis method, due to its simplicity, cost-effectiveness, and precise control. The films were prepared at varying molar concentrations (0.1, 0.15, and 0.2 M) and analyzed for their structural, optical, and morphological properties. X-ray diffraction (XRD) confirmed that all films exhibited a tetragonal crystalline structure with a preferred orientation along the (101) plane. The crystallite size, calculated using the Scherrer equation, reached a maximum of 27.26 nm at 0.2 M concentration, indicating improved crystallinity with higher concentration. Optical studies revealed a decrease in transmittance and an increase in absorbance in the visible region as the concentration increased, accompanied by a reduction in the optical band gap from 3.84 to 3.57 eV and an increase in Urbach energy. Scanning Electron Microscopy (SEM) images showed that the films had a dense and smooth morphology, while Energy Dispersive X-ray (EDX) analysis confirmed the elemental presence of zirconium and oxygen in the films.