金属离子掺杂纳米SnO_2材料的气敏性能及掺杂机理

Gas Sensitivity and the Mechanism of Nano-SnO_2 Doped by Metallic Ions

以SnCl4·5H2O为原料合成纳米SnO2，并以其为基底材料分别以离子形式掺杂Ag^＋、Ni^2＋、Ce^3＋、Sb^2＋等作为气敏材料，制作旁热式气敏元件．研究了其对甲醇、乙醇气体的气敏性能．结果发现，适量的金属离子掺杂可提高SnO2的气敏性能，其中掺Ag^＋效果最佳，可显著提高SnO2对甲醇、乙醇气体的灵敏度．在工作温度为360℃时，对体积浓度为400×10^-6的乙醇、甲醇气体灵敏度分别为121和66．掺Sb^2＋可提高SnO2的导电性，在温度为200℃时，电阻值由180kΩ降至4kΩ．用Materials Studio软件对掺杂不同金属的SnO2的能带结构进行了理论计算，分析表明，掺杂使SnO2能带带隙宽度由掺杂前的2．65eV减少为2．02～2．62eV，相应元件电阻阻值的减少与带隙宽度变化趋势一致，带隙宽度是影响SnO2传感器工作温度高低的重要因素．

Nanosized SnO2 gas material was prepared with SnCl4·5H2O as raw materials. The indirect heating gas sensors were prepared using nano-SnO2 doped by metallic ions including Ag^＋, Ni^2＋, Ce^3＋ and Sb^2＋. Gas sensitivity of the SnOE-based sensor to ethanol and methanol was studied. The results show that gas sensitivity of SnO2 is improved by doping proper metallic ions, moreover, the sensitivity to ethanol and methanol is remarkably enhanced by adding Ag^＋, which is 121 and 66, respectively with gas volume concentration of 400 × 10^-6 at 360 ℃. The conductivity of SnO2 doped by Sb^2＋ was improved and the resistance of the sensor decreased from 180 kΩ to 4 kΩ at 200 ℃. The band structures of SnO2 doped by different metallic ions were calculated with Materials Studio software. The results indicate that the band gap of SnO2 reduces from 2.65 eV to 2.02--2.62 eV by doping metallic ions and the resistance decreases with the change of the band gap. The band gap is a crucial factor to affect operating temperature of SnO2 sensor.