Considering the issues being caused by various gases which are emitted in the environment and can cause lethal damage to humans and environment, proper sensors are to be deployed for detection. So, gas sensors with excellent efficient sensitivity and stability are required. Before few years mixed oxides are used in pollution control via adsorption and/or catalysis, they are also frequently superior to simple oxides with regards to the catalytic performance, long lifetime and resistance to sintering [1]. Among different metal oxides, zinc oxide (ZnO) is the most preferable candidate because its wide band gap (3.37 eV), enhanced electron mobility of 200 cm²/V s [2, 3], good chemical and thermal stability [2], photoelectric response and tunable transport properties [4]. In addition, it is robust, has a fast response with a possibility of miniaturization [5]. However, it presents some disadvantages, such as the high working temperature, between 400 and 500 C, poor gas selectivity and comparatively low gas sensitivity [5, 6]. In general, to improve sensor performances the control of material morphology, doping by additives which act as a catalyst for the solid-gas reaction [7] are an issue and the use of multiple oxide heterostructures may also be another effective mean that may have been used [6].

Undoped and 0.002, 0.006 and 0.008 molar concentrations of Mg, Ag and Mn, respectively, doped and co-doped ZnO/ZnAl₂O₄ thin films are successively deposited on Si substrate by chemical spray method. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed that ZnO: Mg Ag/ZnAl₂O₄ coating has the best crystallinity and the lower estimated electrical resistance. Response and the gaz sensing characteristics of the mists are discussed.

References

[1] El-Nabarawy Th, Attia A.A, Alaya M.N, Mater Letter, 24 (1995), 319-325.

[2] N. Yamazoe, G. Sakai, K. Shimanoe, Catalysis Surveys from Asia, 7 (2003), 6375.

[3] Q. Xiang, G. Meng, Y. Zhang, J. Xu, P. Xu, Q. Pan, W. Yu, Sensors and Actuators B, 143 (2010), 635640.

[4] A. J. Kulandaisamy, J. R. Reddy, P. Srinivasan, K. J. Babu, G. K. Mani, P. Shankar, J. B. Balaguru Rayappan, Journal of Alloys and Compounds, 688 (2016), 422-429.

[5] M. Hjiri, L. El Mir and S. G. Leonardi, Chemosensors, 2 (2014), 121-130.

[6] Kapse V, Research Journal of Chemical Sciences, 5 (8) (2015), 7-12.

[7] Y. Jianhui, Z. Li, L. Xiaoyan, Z. Xiuxiu and D. Chaohua, Chemical Science Review and Letters, 3: 12 (2014).