Preparation Of Rare Earth(Ho³⁺,Ce³⁺)doped SnO₂ Nanomaterials And Study On Their Gas-sensitive Properties

With the rapid development of modern science and technology,the problem of air pollution is becoming more and more serious.Semiconductor gas sensors have been widely used to detect inflammable,explosive,toxic and harmful gasses due to their long life,low cost,wide detection material with high electron mobility,and SnO₂gas sensor has a wide detection range and good chemical stability.However,many methods are needed to solve the shortcomings of pure SnO₂ based gas sensors,such as poor stability,slow response speed,poor selectivity,etc.The main contents of this paper are as follows:1.In this work,SnO₂ nanoparticles（NPs）with different holmium ions concentrations of 0 at.%,0.11 at.%,0.45 at.%,and 0.53 at.%have been synthesized by a gas-liquid phase chemical deposition method with following annealing process.The SnO₂:Ho³⁺NPs exhibit superior triethylamine（TEA）gas sensing properties.The TEA sensing performance of the 0.45 at.%Ho-doped SnO₂ NPs based sensor markedly improve compared with other different Ho doped based sensors.The response time for detecting 50 ppm TEA is only 2 s,and the response value is about12.The as fabricated sensor shows fast response,excellent selectivity and reproducibility to TEA gas at a relatively low working temperature of 175 ^oC.Gas sensing testing shows that a suitable concentration of Ho doping leads to the enhancement of the sensor response.The enhanced sensing mechanism is attributed to the formation of oxygen vacancies and change of carrier concentration.2.The SnO₂ with Ce³⁺doping concentrations of 0 at.%,0.19,0.47 and 0.62 at.%were synthesized by gas-liquid phase chemical deposition and annealing.SnO₂:Ce³⁺NPs shows excellent formaldehyde gas sensing performance.At the working temperature of 235 ^oC,the doping concentration is 0.47 at.%SnO₂:Ce³⁺,and the response value of the gas sensor to the formaldehyde gas of 50 ppm is 15 and the response/recovery time is 1/61 s,with the detection limit as low as 1 ppm.Compared with pure SnO₂,the gas sensitivity of formaldehyde is significantly improved.According to the theory of electron depletion layer and the variation of carrier concentration and oxygen vacancy,the gas-sensitive mechanism is explained.