Surface characterization study on SnO2 powder modified by thiourea

The SnO2 material prepared by sol–gel method was modified by thiourea solution in different concentrations (0.05, 0.1 and 0.2 mol dm−3). Then the structure and the average grain size of the SnO2 material were investigated by X-ray power diffraction. In order to understand the nature of the species on the SnO2 surfaces, the thermal gravimetric and differential thermal analyzer (TG–DTA) and IR spectra of these modified and unmodified sample were taken. The result indicates that the stability of oxygen adsorbed on thiourea-modified surface was improved and the amount of surface hydroxyl groups adsorbed on this grain surface was decreased. The thiourea adsorbed on SnO2 grain surface is translated to SO42− after sintered at 600 °C. SO42− species stabilize the resistance of the SnO2 sensor.