| "Green house effect",indoor environment and photosynthesis etc have made it be an important and necessary research project that using CO2 sensor to detect and control CO2 concentration in the atmosphere. In this paper, the CuO-SrTiO3 and CuO-BaTiO3 conductive type composite-metal oxide thin films were researched as a new kind of CO2 sensor material. The preparation of the sol and thin film, gas-sensitivity, sensitivity mechanism of the composite-metal oxide thin films were studied systematically.The CuO-SrTiO3 and CuO-BaTiO3 thin films were successfully prepared by a noval sol-gel method, which used inorganic salt as starting materials, used citric acid as chelating agent and glycol as cross-linkage agent. The analysis of FI-IR spectra, XRD patterns and SEM morphologies reveal that citric acid cheletes metal ions, glycol is a cross-linkage in CuO-SrTiO3 and CuO-BaTiO3 sol solution. The concentration of sol solution was found to have a great effect on formation of thin films. The 0.1mol/L sol was testified to prepared thin films appropriately when high or low concentration fail to develop eligible films.The CO2 gas sensing characteristic of CuO-SrTiO3 and CuO-BaTiO3 thin films have been studied. CuO-SrTiO3 thin films exist metalloid-semiconductor transition with the temperature changed. Its very low resistance-temperature coefficient above 300℃ is deal to the metallic conductivity.The CuO-SrTiO3 thin films have a strong sensitivity and choice to CO2 with Ag doped. The gas-sensing characteristic of CuO-SrTiO3 thin films has been improved by noble-metal Ag and metal ion Mg2+ or Zr4+. With doping noble-metal Ag and metal ion Sr2+, the gas-sensing characteristic of CuO-BaTiO3 thin film was optimized. At last, the sensitivity mechanism of CuO-SrTiO3 and CuO-BaTiO3 thin film were explained by p-n junction and adsorption theory.
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