CAPACITIVE-TYPE GAS SENSOR FOR THE SELECTIVE DETECTION OF CARBON-DIOXIDE

The capacitances of CuO mixed with BaSnO3, SrTiO3, CaTiO3, and ZnO are dependent on the CO2 concentration, similarly to that of CuO-BaTiO3. In particular, the mixed oxide CuO-SrTiO3 is more sensitive to CO2 tha n CuO-BaTiO3, and the mixed-oxide capacitor CuO-BaSnO3 is promising fo r sensing CO2 over a wide range of concentrations. Moreover, addition of Ag to CuO-BaTiO3 mixed oxide is effective for enhancing the sensiti vity to CO2. The sensitivity (C(CO2)/C(air)) to 2% CO2 Of Ag-added Cuo -BaTiO3, which has been calcined at 700-degrees-C followed by operatio n for 60 h, is as high as 70.