Surface characterization and H2S-sensing potential of iron molybdate particles produced by supercritical solvothermal method and subsequent oxidation

The mostly crystalline polymorph beta-FeMoO4 was prepared by solvothermal synthesis from organic precursors, followed by high temperature supercritical drying in an autoclave. Crystallization of the synthesized particles occurred during subsequent heat treatment at 350 degrees C, confirmed by X-ray diffraction pattern analysis. The presence of Fe3+ ions in the powder, both well-crystallized and amorphous after heat treatment at 500 degrees C, was confirmed by room temperature Mossbauer spectrum. Thick-film gas sensors were prepared by conventional hand coating of a paste, the Fe-2(MoO4)(3) powder mixed with an alpha-terpineol-based solvent, over the Au electrodes. The response of the prepared sensors to H2S gas in the low concentration range 1-10 ppm in air was investigated. Moderately fast response and recovery times were observed. The iron molybdate, produced at low temperature, may be successfully used in the preparation of a H2S gas sensor.