Rapid evaluation processes for candidate CO and HC sensor materials; Examination of SnO2,Co3O4, and CuxMn3-xO4 (1<x<=1.5)

To overcome the difficulty in determining which new metal-oxide materials may be useful as carbon monoxide or hydrocarbon sensors, a rapid evaluation process using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) has been developed. Three basic response modes, absorptive, electrochemical, and thermistor, are herein described for metal-oxide materials. Data from the evaluation experiments can provide evidence that one or more of these response modes is active for a given material. For illustration, the well-known sensor material SnO2 has been examined, along with Co3O4 and a new sensor candidate, CuxMn3-xO4 (1 < x less than or equal to 1.5). Four-point probe electrical evaluations have also been performed on the latter material, with results showing a linear signal dependence to CO in air from 10% to 1000 ppm.