Gas sensor is an important branch of sensor field, WO₃ as an n-type semiconductor material is a gas-sensitive material with high sensitivity, especially for nitrogen oxides, hydrogen sulfide, ammonia, hydrogen and other gases. Research and application and other aspects of WO₃ sensitive material has made great development, while some difficulties are needed to overcome. Such as, the sensitivity sensor has low sensitivity at low concentration, requires a high temperature, response and recovery for a long time, insufficient in stability, repeatability poor and other shortcomings.

 

Doping can overcome some difficulties, especially rare earth doped WO₃ gas sensor have an obvious improvement, the majority of it is due to the role of grain refinement, a modified surface, formed by doping impurity defects in materials and improve conductivity, etc., thus effectively improving the performance of WO₃ gas sensing. Cerium is the rare earth element which belongs to the ΙΙΙ vice ethnic lanthanides, a silver-gray active metal. This article proposes a method using sol – gel to prepare cerium-doped nano WO₃ gas sensor, and study its properties; prepared as follows:

1. Add an appropriate amount of ammonium paratungstate into distilled water, then dissolved at 70°C with the ultrasonic wave to get the solution which appears in the state of weak acid;

2. Adjust the solution described above with ammonia which the molar concentration is 3mol/L until the pH value turns to 7 ~ 9;

3. Add the appropriate amount of cerium nitrate ethanol solution dropwise into the solution above to obtain a white viscous sol;

4. Adjust the above-described sol with nitric acid to pH value of 2-4, then heated evaporation for 30 minutes, until the sol was concentrated to 20 ~ 25mL, to generate a white gel;

5. Transfer into blast drying oven at 80 ° C for 1 hour and then calcined at 500 degrees Celsius in a muffle furnace for 1 hour to obtain Ce-doped nano WO₃ powder.

 

Analysis showed that tungsten trioxide doped with the different amount of Ce has variety of degrees on the sensitivity of the ethanol, benzene, toluene, formaldehyde, CO, etc., such as pure WO₃ has the sensitivity of more than 2600 on hydrogen sulfide, while it is not more than 10 on the other gases, WO₃ nanoparticle of 1% of cerium doped has the better sensitivity than the other amount of Ce doped, wherein the NO sensitivity is up to 360, ect.. In addition, Ce doped of WO₃ gas sensor does better in the resistance to moisture.