Study on microstructure and gas sensitivity of Au-doped WO₃-based composite coating used in gas sensor

To improve the accuracy of gas sensor, the Au-doped WO₃-based (WO₃/Au) composite coatings were prepared by the plasma spraying process, and the microstructure and gas sensitivity were analyzed. The results show that, only two diffraction peaks, corresponding to Au and WO₃, are formed in the X-ray diffraction patterns of the WO₃/Au composite coatings, and no other phase diffraction peaks are generated. Compared with the pure WO₃ coatings, the WO₃/Au composite coatings do not significantly change in the particle size, crystallinity, and microstructure. The separation phenomenon occurs in the desorption curve of the WO₃/Au coatings, which results in the desorption lag. When the temperature rises, the response values of the pure WO₃ coatings and the WO₃/Au composite coatings used in gas sensors rise to the peak and then gradually decrease, and the maximum value appears at 300℃. Compared with the pure WO₃ coatings, the WO₃/Au composite coatings used in gas sensors can achieve the rapid response to NO₂ and obtain the shorter recovery time, showing the better gas sensitivity of WO₃/Au composite coatings.