Preparation of Gas Sensors with Nanostructured SnO2 Thick Films with Different Pd Doping Concetrations by an Ink Dropping Method

Pd-doped SnO 2 thick film with a pure tetragonal phase was prepared on patterned Pt electrodes by an ink dropping method.Nanostructured SnO 2 powder with a diameter of 10 nm was obtained by a modified hydrazine method.Then the ink solution was fabricated by mixing water, glycerol, bicine and the Pd-doped SnO 2 powder.When the Pd doping concentration was increased, the grain size of the Pd-doped SnO 2 thick film became smaller.However, an agglomerated and extruded surface morphology was observed for the films with Pd addition over 4 wt%.The orthorhombic phase disappeared even at a low Pd doping concentration and a PdO peak was obtained for a high Pd doping concentration.The crack-free Pd-doped SnO 2 thick films were able to successfully fill the 30 µm gap of the patterned Pt electrodes by the optimized ink dropping method.The prepared 3 wt% Pd-doped SnO 2 thick films showed monoxide gas responses (R air /R CO ) of 4.0 and 35.6 for 100 and 5000 ppm, respectively.