Trace level detection of NH₃ at room temperature using Cd-ZnFe₂O₄ thin films

This study focuses on developing economical and efficient ammonia (NH₃) gas sensors capable of detecting low concentrations at room temperature. Cd-doped ZnFe₂O₄ (Cd_xZn_1-xFe₂O₄, x = 0, 0.1,0.3, and 0.5) thin films were deposited via spray pyrolysis, showing significantly enhanced sensing performance compared to undoped ZnFe₂O₄. The Cd_0.5Zn_0.5Fe₂O₄ (ZFCD5) film demonstrated the best response (∼8) at 1 ppm NH₃, with fast response (105 s) and recovery (54 s) times, a sensitivity of 10.07 ppm^-1, repeatability, selectivity, and more stability over 6 weeks. The improved sensing is attributed to the angular-rod-like morphology that increases active sites and enhances charge transfer. Cd incorporation effectively boosts defect density and adsorption-desorption efficiency, resulting in a 10-fold higher response than the undoped film (∼0.8). The findings highlight the potential of Cd-doped ZnFe₂O₄ thin films as promising, room temperature NH₃ sensors for industrial, environmental, and safety applications, also supporting safer environments for individuals with disabilities.