中文摘要：

以La2O3、Cr（NO3）3·9H2O、Sr（NO3）2、Mn（NO3）2和柠檬酸为原料，用溶胶-凝胶法制备了La0.75Sr0.25Cr0．5Mn0.5O3粉体。使用DTA、XRD、SEM、FT-IR等对粉体及中间体进行了表征。结果表明，用此法制备的前驱体，经700℃焙烧2h即可制得粒度均匀的晶体，其平均粒径为4．87nm。以制得的粉体为气敏材料制备了管状NO2气体传感器，并测试了传感器的性能。结果表明，La0.75Sr0.25Cr0.5Mn0．5O3材料对NO2具有良好的敏感性能。在一定温度范围内，随着NO2浓度的升高，传感器电动势信号逐渐增大。在测试温度范围内，电动势与NO2浓度之间呈良好的线性关系。

英文摘要：

La0.75Sr0.25Cr0.5Mn0.503 powders were prepared by sol-gel method using La2O3, Cr（NO3）3 · 9H2O, Sr（NO3）2, Mn（NO3）2 and citric acid as raw materials. The powders and dry gel were characterized by means of DTA, XRD, SEM and FT-IR. The results show that the powders exhibited an homogeneous phase with particle size of 4.87nm after calcined at 700℃for 2h. The prepared powders were used as the gas sensing materials for the fabrication of tubular NO2 sensor, and sensing performances is tested. The results show that the La0.75Sr0.25Cr0.5Mn0.5O3 exhibits high sensitivity to NO2 gas. The relationship between EMF and NO2 concentration is linear.