化學(xué)專業(yè)外文資料翻譯--具有高靈敏度的甲醛氣體傳感器的制備及其氣敏特性(完整版)
【正文】 ensitive body based on In2O3 was approximately mm after calcination. In order to improve their stability and repeatability, the gas sensors were aged at an operating temperature of 150 .C for 150 h in air. The sensor resistance was measured by using a conventional circuit in which the element was connected with an external resistor in series at a circuit voltage of 5 V. The gas response β was defined as the ratio of the electrical resistance in air (Ra)to that in gas(Rg). 3. Results and discussion Sensing properties of CdO–In2O3 material calcined at 650 .C is better than those at 500, 750, and 850 .C. In this paper, we mainly discuss the material calcined at 650 .C. The Xray powder diffraction patterns for the asprepared and calcined materials are shown in Fig. 1. The peaks of In2O3 and CdO are observed in the pattern of the sample calcined at 650 .C for 1 h. The pattern is indexed as In2O3 (JCPDS No. 060416) and CdO (JCPDS No. 652908), and shows a high degree of crystallinity. CdCO3 will be deposed and CdO be formed at400 .C [14]. The phase of In2O3 is not changed and other new phase (for e xample, CdIn2O4) is not observed after calcining at 650 .C. On the other hand, the width of XRD peaks of In2O3 Fig. 1. The XRD patterns of asprepared and calcined materials: (a) CdCO3 (JCPDS No. 421342), (b) In2O3 (JCPDS No. 060416), and (c) CdO (JCPDS No. 652908). does not change before and after calcination, revealing that the CdO can effectively inhibit the crystalline grain growth [15]. The crystallite average sizes calculated according to Scherrer’s equation are about 28 nm for In2O3 before calcination, and about 30 nm for In2O3 and 31 nm for CdO after calcination. Comparing with the XRD results, SEM images revealed that there were various sizes of particles in the asprepared and calcined samples. The large particles were posed of small crystallites. Fig. 2(a) and (b) shows SEM images of the asprepared and calcined materials, respectively. Most particles have irregular morphology, and the particle size is in the range of 100–500 nm. It has been addressed that the electrical conductivity of a sensor depends on the gas atmosphere, but also on the operating temperature of the sensing material exposed to the test gas [16]. Fig. 3 depicts the relation between the response and the operating temperature for — 44 — the sensor. The operating temperature has a great influence on the response. Interestingly, the response first increases gradually and then decreases with increasing the operating temperature. It can be seen that the CdO–In2O3 based sensor shows excellent gassensing characteristics to formaldehyde gas in the low temperature range. It exhibited the highest response to formaldehyde gas at 95 . low operating temperature is an advantage in application. As shown in Fig. 4, the response of the CdO–In2O3 based sensor operated at 95 .C shows good dependence on the gas concentration. The sensor exhibits very sma
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