NOx sensitivity of conductometric In(OH)3 sensors operated at room temperature and transition from p- to n- type conduction

Non-single crystal cubic In(OH)3 with porous structure was synthesized by hydrothermal method. It is well known that In(OH)3 is an n-type semiconductor, but freshly prepared In(OH)3 displays p-type conduction behavior according to response towards testing gases. Furthermore, the In(OH)3 sensor displays n-type conduction behavior after it was induced by the high concentration of NOx and the induced In(OH)3 sensor is named IIHS. The gas sensing properties of the IIHS with the concentration of NOx ranging from 100 ppm to 10 ppb were investigated at room temperature, and the IIHS displayed numerous advantages in the aspects of great reliability and high sensitivity. The mechanism of n-p-n conductivity conversion process of In(OH)3 was investigated and proposed by XPS and in situ DRIFT.