Development of Methane Gas Sensor by Various Powder Preparation Methods

After SnO₂ fine powder was prepared by precipitation method, Ca as crystallization inhibitor and Pd as catalyst were added to SnO₂ raw material by various methods. Thick film device was fabricated on the alumina substrate by mixing ethylene glycol and such mixed powders. The sensing characteristics of the device for methane gas were investigated. The most excellent gas sensing property was shown by the thick film device fabricated by Method 3 in which Ca and Pd doped SnO₂ powder is prepared by mixing SnO₂ powder, 0.1 wt% Ca acetate and 1 wt% PdCl₂ in deionized water and by calcining the mixture, after Sn(OH)₄ is dried at 110℃ for 36h. The sensitivity of the sensor fabricated with SnO₂-0.1 wt%Ca acetate-lwt%PdCl₂ powder (Method 3) powder heat-treated at 700℃ for lh was about 86% for 5,000 ppm methane in air at 350℃ of the operating temperature. Response time and recovery were also excellent.