Ethanol-sensing characteristics of cadmium ferrite prepared by chemical coprecipitation

The microstructure, electrical property and gas-sensing characteristics of complex compounds in the CdO-Fe2O3 system have been investigated. Raw powder with Cd/Fe = 1:2 was prepared by chemical coprecipitation method. The results from thermal gravimetric-differential thermal analysis and X-ray diffraction measurement indicate that decomposition of CdCO3 takes place from 350 to 500 degrees C, and the solid reaction in CdO-Fe2O3 system starts at 570 degrees C; the completion of this reaction is up to 800 degrees C. Single phase of CdFe2O4 is composed of spheroidic grains with narrow size distribution between 50 and 150 nm. Sample calcined at 650 degrees C consists of smaller grains with different shape and sizes due to the presence of three phases, i.e., CdFe2O4, CdO and alpha-Fe2O3. The sensors based on Cd-Fe complex oxides show a high sensitivity and selectivity to C2H5OH gas over CO, H-2 and i-C4H10. The sensor made of 650 degrees C sample operates at 380 degrees C, and its sensitivity to 200 ppm C2H5OH gas is up to 90, but its sensitivity to 1000 ppm H-2, CO or i-C4H10 are only 7.5, 4 and 5, respectively. (C) 1999 Elsevier Science S.A. All rights reserved.