Research Of Low-resistance And High-performance Acetone Sensor Based On CdSnO₃ Nanocrystals

The development of science and technology in today’s era is very rapid.Technology not only brings convenience to people’s lives,but also makes people’s lives more comfortable.However,the combustion of fossil fuels,industrial production,and toxic and harmful gases emitted from decoration materials will inevitably damage the atmospheric environment and cause health hazards to the human body.In order to effectively and quickly detect toxic and harmful gases,as the core part of gas sensors,sensing materials have always been a research hotspot in the field of sensing.Among them,the metal oxide semiconductor material has a simple synthesis method,low cost,and excellent gas sensing performance.However,traditional n-type metal oxide semiconductors,such as WO₃,SnO₂,etc.,have low electrical conductivity,especially under the influence of humidity,the response/recovery time is very long,and the response value decreases greatly with the increase of relative humidity.In view of the above problems,in this paper,a perovskite semiconductor oxide CdSnO₃was synthesized,and combined with noble metal doping modification,the fabrication of an acetone sensor with low resistance,high sensitivity,good moisture resistance,and fast response/recovery was realized.The main research contents are as follows:（1）First,CdSnO₃nanoparticles are prepared by solvothermal method according to stoichiometric ratio combined with high temperature calcination.The noble metal Pd is further used for doping,and the optimal doping amount is discussed based on the measurement results of gas sensing characteristics.The results show that the undoped noble metal CdSnO₃nanoparticles have a mixed phase structure ofα-ilmenite andβ-perovskite.The doping of noble metals not only makes theα-ilmenite phase disappear,the optimal operating temperature decreases,and the response value of the sensitive element increases gradually with the increase of doping amount,and the sensitivity reaches the maximum when the doping amount of Pd reaches 8 at%.Compared with the undoped device,the response of the device to 100 ppm acetone（20.3）was improved by a factor of 3.2 when doped with 8 at%Pd,and the baseline resistance of the device was only 12.6kohm.Moreover,the fabricated sensor has a fast response/recovery time（2 s/12 s）,and can respond significantly to acetone gas as low as 0.2 ppm,with a response value of 1.2.（2）According to the above experimental results,the effect of excess CdCl₂on the crystal form and gas-sensing properties of the prepared product was further studied.The study found that when the addition of CdCl₂exceeds 5 at%of the stoichiometric ratio,theα-ilmenite phase belonging to CdSnO₃disappears;when the amount of Cdis further increased to exceed 10 at%of the stoichiometric ratio,the phase of Cd₂SnO₄appears.This indicates that more crystallineβ-perovskite CdSnO₃nanoparticles can be synthesized by adding 5 at%Cdbeyond the stoichiometric ratio during the synthesis.Compared with the CdSnO₃material prepared at the stoichiometric ratio,the response to 100 ppm acetone changed from 6.3 to 17.8,indicating that the pure phaseβ-perovskite CdSnO₃structure contributes to the improvement of sensitivity.On this basis,different amounts of Pd-doped CdSnO₃nanoparticles were prepared.The results show that the sensitivity of the sensor gradually increases with the increase of Pd doping content,and when the Pd doping content reaches 3 at%,the sensitivity reaches the maximum value,and the response value to 100 ppm acetone gas reaches 36.6,which is significantly higher than that of the undoped sensor.The response value of the CdSnO₃sensor（17.8）,the response/recovery time is 2s/8 s.Moreover,the response value of the sensor is also higher than that of the sensor prepared by the optimal Pd-doped（8 at%）CdSnO₃nanoparticles under the stoichiometric ratio,and the usage of noble metal is also greatly reduced.In the relative humidity range of 20%-98%,the response value of the 3 at%Pd-doped CdSnO₃sensor changed from 36.6 to 27.1,a decrease of only 26.0%,and the baseline resistance decreased by 25.4%,which is better than that of the undoped CdSnO₃Powder（response value decreased by 49.0%,baseline resistance decreased by 59.4%）,Pd-doped8 at%CdSnO₃nanoparticles when Cddid not exceed stoichiometric ratio（response value decreased by 56.7%,baseline resistance decreased by 29.7%）and commercial SnO₂powder body（53.5%decrease in response value and 66.0%decrease in baseline resistance）.The recovery times of 3 at%Pd-doped CdSnO₃,pure-phase CdSnO₃,and commercial SnO₂powders are 8s,10s,and more than 100 s,respectively.The above results show that the crystal structure has a significant effect on the gas sensing properties.The pure phase-basedβ-perovskite CdSnO₃has higher sensitivity to acetone gas,and only a small amount of noble metal modification can make the sensitivity of the sensing element reach.At the same time,Pd doping can effectively improve the humidity resistance,response value and recovery speed of the sensor.