Micro Semiconductor CO Sensors Based on Indium-Doped Tin Dioxide Nanocrystalline Powders

The precursors of SnO(2) or In(2)O(3)/SnO(2) nanocrystlline powders have been prepared by the sol-precipitation method. The precursors were calcined at different temperatures to prepare SnO(2) or In(2)O(3)/SnO(2) nanocrystalline powders with different particle sizes. The nanocrystallites were examined by differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). And then thick film CO sensors were fabricated using prepared SnO(2) or In(2)O(3)/SnO(2) nanocrystlline powders loaded with PdO(x). The composition that gave the highest sensitivity for CO was in the weight% ratio of 5 wt.% In(2)O(3)/SnO(2):PdO(x) as 99:1(wt %). The composite material was found sensitive against CO at the working temperature 200 °C. It was found that the sensors based on In(2)O(3)/SnO(2) nanocrystalline system exhibited very short response time to CO at ppm level. These characteristics make the sensor to be a promising candidate for detecting low concentrations of CO.