Physicochemical investigation of pure cadmium hydroxide Cd(OH)2 and Cd(OH)2–CdO composite material deposited by pneumatic spray pyrolysis technique

This paper investigates the physicochemical properties of pure Cd(OH)2 and Cd(OH)2–CdO composite materials in depth. The cadmium sulfate octahydrate (3CdSO4.8H2O) is used as a precursor for the first time in this work and never been used in previous works involving cadmium-based materials. Additionally, we present the first synthesis of Cd(OH)2–CdO by pneumatic spray pyrolysis deposition technique. Five cadmium hydroxide–oxide films are coated by spray pyrolysis on glass substrates by varying the solution concentration (0.025 M, 0.05 M, 0.1 M, 0.2 M, and 0.3 M). According to the structural characterization, the molarity has a clear impact on the formation of pure Cd(OH)2 or Cd(OH)2–CdO phase mixture. The UV–Vis spectrophotometry reveals the high film transparency of ~ 90% in the visible region. The calculated optical bandgap of Cd(OH)2 and CdO for the various films corresponds well to the literature. The FTIR analysis reveals the characteristic bands of Cd–O and the presence of –OH groups as the main signature of Cd(OH)2. The elemental composition investigated by means of EDS confirms the presence of Cd and O. The photoluminescence characterization reveals the various electronic transitions within CdO, considered as an activator within the Cd(OH)2 host matrix. For the lowest molarities, SEM micrographs reveal a distinct porous structure. The electrical measurements revealed that the films’ resistivity varies in the range (3–5.5) Ω.cm.