A novel high performance ethanol gas sensor based on CdOFe2O3 semiconducting materials
Introduction
Ethanol gas sensors have taken notice of their practical significance. Though (β-CdSnO3, ZnSnO3 and Fe2O3 have been extensively studied as ethanol gas-sensing materials 1, 2, 3, their sensitivity and selectivity to ethanol are still dissatisfactory. Recently we have found that CdO addition into Fe2O3 can dramatically enhance its gas sensing characteristics. An investigation on the influence of preparation conditions on the conductivity and gas sensing property of the materials was addressed. In this paper we present the electrical conduction mechanism and excellent ethanol gas-sensing performances of the CdOFe2O3 materials with the optimal composition.
Section snippets
Experimental
A series of mixed salt solutions with different Cd/Fe molar ratios were prepared by dissolving analytically pure CdSO4·8/3H2O and Fe(NO3)3·9H2O into distilled water. The ultramicro powders of CdOFe2O3 system were obtained by co-precipitating the mixed solutions with aqueous ammonia as the precipitant, and then drying, grinding and calcining at different temperatures.
Gas sensing elements of external-heated type were fabricated by a thick film technique in which a paste made of proper CdOFe2O3
Electrical conduction mechanism of CdOFe2O3 system
Fig. 1 shows the plots of the conductance versus temperature of an element in different ambient atmospheres. The conductance in argon gas increases monotonously with temperature, showing the typical characteristics of a n-type semiconductor, and is about two orders of magnitude higher than that in either air or oxygen. The much lower conductance value in the oxygen-containing atmosphere is associated with the oxygen adsorbed on the material surface, which captures electrons from the bulk
Conclusions
A new ethanol gas sensor based on CdOFe2O3 complex oxide semiconducting material has been developed. The sensor is of surface-controlled gas-sensing mechanism and exhibits very good performance and characteristics:
- 1.
High sensitivity with a linear behavior to ethanol in the concentration range from 100 to 1000 ppm;
- 2.
Excellent selectivity to ethanol against other common gases which may co-exist with ethanol, such as petrol, H2, CO, LPG and other hydrocarbon gases;
- 3.
Good stability and durability of the
Acknowledgements
The authors wound like to thank the Chinese National Natural Science Foundation for its financial support.
Xingqin Liu was born in 1945. She is the professor and project director of ‘Gas Sensing Materials’ (USTC). She graduated in inorganic chemistry from USTC in 1969 and was a visiting scientist at R. & D. Lab of Hitachi Chemicals Co. (Japan, 1988–89) and Twente University (The Netherlands, 1991–92). Her research fields include gas-sensing semiconducting materials and devices, advanced ceramics and ionic electronic mixed conductors and has had over 25 papers published.
Zhengliang Xu was born in 1972
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Xingqin Liu was born in 1945. She is the professor and project director of ‘Gas Sensing Materials’ (USTC). She graduated in inorganic chemistry from USTC in 1969 and was a visiting scientist at R. & D. Lab of Hitachi Chemicals Co. (Japan, 1988–89) and Twente University (The Netherlands, 1991–92). Her research fields include gas-sensing semiconducting materials and devices, advanced ceramics and ionic electronic mixed conductors and has had over 25 papers published.
Zhengliang Xu was born in 1972 and is an engineer of Shenzhen Communication Photometer. He graduated in materials chemistry (M.S.) from USTC in 1997.
Yafei Liu was born in 1968 and is a Ph.D. student in USTC. He graduated in applied chemistry from Tianjin University in 1990 and then was an engineer of Sun Wind Group for 5 years (engaged in fine chemicals & daily chemicals). His research topics include ultra-micro complex oxide semi-conductors and their gas-sensing properties. He is supervised by Professor X.Q. Liu, and Professor Y.S. Shen.
Yusheng Shen was born in 1932. He graduated in inorganic chemistry from Jilin University in 1958. He has been the director of gas-sensing materials group at USTC for over 10 years; the head councillor of Chemical Sensor Division, Chinese Sensor and Transducer Society. His research fields are gas, humidity and thermal sensors and he has had over 120 papers published.