Xing-Hui Wu

Ammonia-sensing characteristics of Pt and SiO2 doped SnO2 materials

Abstract The gas-sensing characteristics of doped SnO2 materials for ammonia were investigated in this paper. A good formula of ammonia sensitive materials has been achieved. The phase of sensitive material was characterized by X-ray diffraction. The gas sensor of indirect heating that was made by this sensitive material had high sensitivity to ammonia gas and stability. Infrared was used to study the reacting products of NH3 on the surface of the material. The sensitive mechanism of sensor was analyzed and discussed.

Preparation and gas-sensing properties of perovskite-type MSnO3 (M=Zn, Cd, Ni)

The MSnO3 semiconducting oxide that can be used as a gas sensitive material for detecting ethanol gas is reported in this paper. MSnO3 powders were prepared by a chemical coprecipitation synthesis method. The preparation conditions were carefully controlled. After calcinations at appropriate temperature, the n-type semiconductor gas-sensing materials were obtained. The phases and microstructures of the obtained powders were characterized by X-ray diffraction (XRD). The products corresponded to a small particle size range of 0.1–0.4 μm and high surface area of 60–65 m2/g. The electrical properties, sensitivity-synthetic conditions and operating temperatures, and selectivity of MSnO3-based sensors were investigated. It was found that sensors had good sensitivity to vapor of C2H5OH. Gas-sensing mechanism was studied with X-photoelectron energy spectra (XPS).

Effects of calcining temperature on lattice constants and gas-sensing properties of Nb2O5

Abstract The effect of different calcining temperatures on the lattice constants of the metal oxide semiconductor Nb 2 O 5 was investigated using powder X-ray diffraction technology. It was shown that the crystal structure, lattice constants and crystallite size were changed with the different calcining temperatures. The electrical resistance and the gas-sensing properties of the gas sensor based on Nb 2 O 5 for petrol, i-C 4 H 10 , H 2 and C 2 H 5 OH gases were different at the different calcining temperatures. The Nb 2 O 5 gas sensor exhibited good sensitivity and selectivity for petrol after calcining at 1000°C.

Synthesis and optical properties of mesostructured titania–surfactant inorganic–organic nanocomposites

Titania–surfactant inorganic–organic nanocomposites with wormhole-like framework mesostructure were synthesized based on self-assembly between a neutral amine surfactant (dodecylamine) and a neutral inorganic precursor (tetrabutyl titanate). The prepared nanocomposites were characterized by x-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR) and x-ray photoelectron spectroscopy (XPS). The optical absorption and photoluminescence spectra have been measured. It has been found that TiO2–surfactant inorganic–organic nanocomposites have a significant red shift of the optical absorption band edge in contrast to that of bulk TiO2, and an unusual room temperature photoluminescence (RTPL). The results obtained indicate that the interfacial effect between the titanium dioxide and the surfactant plays an important role in the optical properties.

Novel high sensitivity and selectivity semiconductor gas sensor based on the p+n combined structure

Abstract In this paper, a new type semiconductor gas sensor of p+n combined structure is reported. The combined structure semiconductor gas sensor is a novel gas sensor that is based on the complementary feedback and complementary multiplication principle (Wu XH. United States Patent 5, 298, 783, 1994; Wu XH. Japan Patent 4-213212, 1992; Wu XH. China Patent 91108927, 1994; Wu XH, Li YF, Zhou ZL, Tian ZH. Chinese J Semicond 1993;14(7):439–44; Wu XH, Li YF, Zhou ZL, Tian ZH. Chinese J Semicond 1994;15(9):643–9; Wang YD, Wu XH. Proc Seventh Int Meeting Chem Sensors. Beijing, China, 1998). The sensor is composed of two sensitive bodies A and B whose conductive types are different. A is a p type material and B is an n type material. The results analyzed from a theoretical viewpoint showed that when A and B satisfied certain conditions, the sensor not only realized multiplication of sensitivity and selectivity, but also had better thermal stability. According to the sensors structure and meeting conditions, we prepared the p+n type gas sensor for C 2 H 5 OH. The experimental results showed that they concurred with theoretical analysis very well.

Study on ZnSnO3 sensitive material based on combustible gases

Abstract In this paper, ZnSnO 3 material prepared with wet synthesis can be used as a gas-sensing material is reported. The sensors of agglomerate type were prepared with ZnSnO 3 material and adulterants, such as noble metals and metal oxides. The experimental results show that the sensors reveal high sensitivity for the detection of combustible gases, and have high selectivity for different gases through the selection of adulterants and the improvement of technology. The sensitive mechanism and failure mechanism of ZnSnO 3 material were discussed.

A new type of semiconductor gas sensor based on the n+n combined structure

Abstract In this paper, a new type of semiconductor gas sensor based on the n + n combined structure is reported. The combined structure semiconductor gas sensor is a novel gas sensor which is based on the complementary feedback and complementary multiplication principle. The sensor is composed of two sensitive bodies A and B whose conductive types are same. A and B are all n type materials. The results analyzed from theoretical viewpoint showed that when A and B satisfied certain conditions, the sensor not only realized multiplication of selectivity, but also had better thermal stability. According to the sensor’s structure and meeting conditions, we prepared the n + n type gas sensor for gasoline. The experimental results showed that they concurred with theoretical analysis very well.

Investigation of reliability and lifetime distribution of the gas sensors based on C2H5OH

Abstract The reliability and lifetime distribution of the indirect-heating gas sensors used for detecting C2H5OH are investigated in this paper. The reliability and the operation-lifetime test are carried out in the way that is the same with other electronic devices. During the long-time operation-lifetime test for over 125 days, the drifts in the sensitivity, selectivity, resistance, and response and recovery time of the sensors are obtained. Through the numerical analysis and data processing of the failure data, the lifetime distribution, distribution parameters, and reliability level are obtained. The curve of the lifetime distribution is the logarithmic normal distribution, and the mean lifetime is 11572 h. The results indicate that the gas sensors have good stability and reliability. They are important for the practical applications and the improvements of the gas sensors performance.

Research on n+p type oxygen sensor

Abstract The thermal stability and sensitivity of a new n+p structure oxygen sensor were studied from the theoretical viewpoint. The results show that when the two sensing materials meet certain conditions, the new type oxygen sensor not only has a higher sensitivity to oxygen than the conventional oxygen sensor (i.e. n-type or p-type single-disc oxygen sensors), but also solves a major problem that the characteristics of conventional oxygen sensors are affected by temperature drift.