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 powde r with Cd/Fe = 1:2 was prepared by chemical coprecipitation method. The res ults from thermal gravimetric-differential thermal analysis and X-ray diffr action measurement indicate that decomposition of CdCO3 takes place from 35 0 to 500 degrees C, and the solid reaction in CdO-Fe2O3 system starts at 57 0 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 distrib ution between 50 and 150 nm. Sample calcined at 650 degrees C consists of s maller grains with different shape and sizes due to the presence of three p hases, i.e., CdFe2O4, CdO and alpha-Fe2O3. The sensors based on Cd-Fe compl ex 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 degr ees C, and its sensitivity to 200 ppm C2H5OH gas is up to 90, but its sensi tivity 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.