The effect of operating temperature on gasochromic properties of amorphous and polycrystalline pulsed laser deposited WO3 films

In this study, tungsten oxide films were synthesized by pulsed laser deposition (PLD) method. The as-deposited films were annealed at a temperature of 250 and 350 °C in air for 1 h. The surface morphology, microstructure, crystalline phase and chemical composition of the as-prepared and annealed films were characterized by SEM, XRD and XPS techniques, respectively. Deposition of Pd nanoparticles onto the tungsten oxide surface was performed by hydrogen reduction of a drop-drying PdCl2 solution onto a WO3 surface at 60 °C. The influence of the annealing temperature on microstructure and gasochromic performance as well as the effect of operating temperature is presented in this work. Results show that the gasochromic responses of the amorphous samples at temperatures below 100 °C has attained approximately a constant value but these values for polycrystalline samples shows a significant increase with increasing temperature and the maximum gasochromic response was achieved at operating temperatures between 90 and 100 °C. Because of the low surface to volume ratio and negligible diffusion length, the polycrystalline film shows intense decrease in ΔODm values compared to the amorphous film at operating temperatures above 100 °C. Also the effect of water desorption at T ∼ 100 °C on gasochromic response was investigated.