SnO_2/LaFeO_3纳米复合材料检测CO时的类受主现象

Acceptor-like behavior during the detection of CO for SnO_2/LaFeO_3 nanocomposite

利用模板法和溶胶-凝胶法分别制备了SnO_2和LaFeO_3纯材料,并检测了纳米复合材料SnO_2/LaFeO_3对CO的气敏性能。在实验过程中,观察到纳米复合材料85%SnO_2+15%LaFeO_3(85Sn-La)及90%SnO_2+10%LaFeO_3(90Sn-La)在检测CO时出现了一个反常现象,通常CO表现为还原性气体的性质,然而在T≤200℃的温度范围内,与CO的作用增加了复合氧化物85Sn-La及90Sn-La的电阻,而这一现象只在与氧化性气体反应时观察过。这种在特定环境下,n型材料与还原性气体(施主)作用时,其导电特征表现为与氧化性气体(受主)作用时相同的现象称为类受主现象。类受主现象只在低温阶段被观察到,且复合氧化物85Sn-La表现最为明显。利用温度、气氛与材料表面的交互作用来解释所观察到的实验现象:在低温情况下,CO与材料表面的吸附氧及羟基发生反应,增加了表面的电荷,降低了材料表面的导电性,因而表现为类受主现象。

Template method and sol-gel method have been used to synthesize SnO2 and LaFeO3, and the CO gas sensing properties of the as-prepared SnO2/LaFeO3 nanocomposites have been studied, During the test, an a nomalous phenomenon has been observed： nanocomposites 85%SnO2 ＋ 15% LaFeO3 （85Sn-La） and 90 %SnO2 ＋ 10 % LaFeO3 （90Sn-La） showed a decreased conductivity towards interaction with CO at temperature lower than 200 ~C, which we call it an acceptor-like behavior. Acceptor-like behavior has been observed at low temperature only and shows a maximum aeceptor effect for nanocomposite 85Sn-La. The interaction between temperature; gas and the material surface has been proposed to explain the observed behavior. At low temperature, a reaction between CO and hydroxyl absorbed on the surface will occur, resulting in the increase of the material surface charge and the decrease of the conductivity.