Traditional ceramic semiconductor gas sensing materials mainly include transition metal oxides, such as SnO2, Fe2O3, WO3, ZnO, In2O3, etc. However, most of these materials are widely used gas sensitive materials with poor gas selectivity. Although the noble metal doping and the improvement of film-making process have improved the gas sensing selectivity, they have increased the cost. Since 1980s, it has been found that gas sensors made of perovskite composite metal oxides such as ZnSnO3 _ 3 and LaFeO3 _ 3 can show good sensitivity. So a lot of research began and became a hot topic in recent years. In this paper, ZnSnO3 was taken as the research object, and the nano-preparation, gas sensing performance and doping modification of this material were studied experimentally. The gas sensing mechanism is also discussed. In this paper, ZnSnO3 precursor was prepared by * * precipitation method, and then perovskite-type composite oxide was synthesized by high temperature roasting. XRD spectrum analysis shows that ZnSnO3 prepared by the new technology of ultrasonic oscillation dispersion and low temperature aging is single-phase structure and there is no impurity phase in the product. The purity of the prepared powder is also higher than that of the powder prepared by the traditional process.
Gas sensitive material
It refers to a functional material whose physical and chemical properties will change with the type and concentration of external gas under certain conditions. At present, the main gas-sensitive materials used are gas-sensitive semiconductor ceramics and polymer gas-sensitive materials;
1. Gas-sensitive semiconductor ceramics. According to the different gas sensing principles, it can be divided into the following three types: ① Semiconductor gas sensing materials are some metal oxides, such as SnO2 and ZnO2. When gas molecules are adsorbed on the surface of this material, its resistance, current or voltage will change sharply. Changing the heating temperature of this material and adding some catalysts (such as Pd, Pt, ThO2) can improve its sensitivity to gas adsorption reaction. ② Contact with sensitive materials of combustion gas. This material is composed of two materials (such as Pt-A 12O3+Pt wire and Pd-A 12O3+Pt wire), one of which generates heat by burning in contact with gas; The resistance of another material (mainly platinum wire) is sensitive to temperature. ③ Solid electrolyte gas sensitive materials. This kind of materials (such as CaO-ZrO2 _ 2, Y2O3-ZrO2 _ 2, etc. ) selectively permeates gas, generates ions in electrolyte, and forms concentration potential.
2. Polymer gas sensitive materials. When this kind of material meets a specific gas, its physical properties will change, such as resistance, dielectric constant, speed and frequency of sound wave propagation on the surface of the material, such as polyisobutylene.
Gas sensitive materials are used as components of gas sensors to detect lunar gas and toxic gas.