Quanxi Cao

Sensing properties of CuO–ZnO heterojunction gas sensors

Abstract CuO–ZnO heterojunction gas sensor is a new type gas sensor and has many advantages, such as low cost, simple processing, and convenient testing, etc. In this work, the sensing properties of these sensors to gases were studied on the condition of different ratios of ZnO to CuO, including the resistance-temperature properties of various samples and their sensitivities and response behavior at different temperatures and in different gases. The obtained results are analyzed and discussed in this paper.

ZnO varistor manufactured by composite nano-additives

Based on the analysis of the effects of ZnO grain boundaries, the new method of manufacturing ZnO varistors prepared by composite nano-additives is put forward in this paper. The emphasis of this technique is mainly on improving the microstructural uniformity and the effects of ZnO varistors grain boundaries so as to obtain the high quality components. As a result of the experiment, fine and active multiplex composite nano-additives are prepared by chemical coprecipitation, and highly uniform microstructure and larger surge absorption capability compared with the conventional oxide mechanical mixed technique are achieved. Moreover, this method is easy to perform and the shape of the obtained powders is apt to control. Also this new technique of manufacturing ZnO varistors is more feasible and of great prevalence in spawning ceramic materials among the existing equipments.

Metal-semiconductor ohmic contact of SnO2-based ceramic gas sensors

The realisation of an ohmic contact between metal electrodes and SnO2 semiconducting ceramics by a metal-n+ -n structure can cancel harmful effects in SnO2 gas sensors that are caused by the unmodified contact. This contact structure does not only increase the sensitivity of SnO2 gas sensors, but also decreases the scatter in gas-response properties of these sensors. Especially, it is necessary to adopt the metal-n+-n electrode structure when ceramic SnO2 gas sensors operate at lower temperatures.

Electrical conduction and oxygen sensing mechanism of Mg-doped SrTiO3 thick film sensors

Abstract The dependencies of the electrical conduction of Mg-doped SrTiO 3 thick film samples on temperature and oxygen partial pressure have been studied. The Mg contents in SrTiO 3 were 10 mol%, 20 mol%, 30 mol%, 40 mol% and 50 mol%, respectively. The experimental results show that all samples exhibit p-type semiconduction in the p O 2 region 3.8×10 −4 –2.6×10 −1 atm and temperature range 500–900°C. The temperature at which a maximal resistance is observed decreases from 300°C to 100°C in Mg-doped SrTiO 3 samples. The 40 mol% Mg-doped SrTiO 3 sample reveals the best oxygen sensing properties. Results are discussed based on the X-ray diffraction and the analysis of defect chemistry.

Effects of Sr2+ or Sm3+ doping on electromagnetic and microwave absorption performance of LaMnO3

The perovskite structure La1−xSr(or Sm)xMnO3±δ (x = 0, 0.25) powders were successfully fabricated by the traditional solid state reaction method. The influences of Sr2+ or Sm3+ doping on the static and dynamic magnetic performance were investigated. The resonance phenomena could be attributed to natural resonance and exchange resonance. The substitution of Sr2+ or Sm3+ into La3+ could greatly influence the resonance frequency. Furthermore, the microwave absorption performance of LaMnO3 was improved after the incorporation of Sr2+ or Sm3+. It is obtained that Sr2+ doped LaMnO3 had superior performance compared with that of Sm3+ doped LaMnO3. The maximum reflection loss was −30.0 dB at 13.968 GHz with a thickness of 1.6 mm. The microwave absorption performance was attributed to both the dielectric and magnetic losses.

Solution combustion synthesis and luminescence properties of (Y,Gd)Al3(BO3)4:Eu3+ phosphors

Abstract Ultrafine Y 0.95- x Gd x Eu 0.05 Al 3 (BO 3 ) 4 phosphors with different Gd 3+ concentrations were prepared by a solution combustion method, and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM). Results showed that the pure phase of YAl 3 (BO 3 ) 4 was obtained at 1000 °C and the prepared particle size varied with calcining temperatures. Photoluminescence spectra indicated that the dominant emission peak was observed at 612 nm due to the 5 D 0 → 7 F 2 transition of Eu 3+ . The luminescence intensity of Eu 3+ was affected by concentration of Gd 3+ in the Y 0.95- x Gd x Eu 0.05 Al 3 (BO 3 ) 4 host and the optimum concentration of Gd 3+ was x =0.75.