Synthesis of new compound semiconductors in the Sn-W-O system for gas-sensing studies

Screen printing has been used to fabricate thick films of various compound and mixed oxides in the Sn-W-O system for gas-sensing studies. The powders for the thick-film pastes were made by heating in vacuum various mixtures o f SnO and WO3 powders, corresponding to the nominal formula Sn(x)Wo(3+x). H ere we have studied the mixed oxide system of tin and tungsten with the ato mic ratio x between 1.25 and 2.5. Two new semiconducting compound structure s (undocumented phases) were synthesized in this composition range between tin and tungsten. A sedimentation method was used for an enrichment "cleani ng" of a particular phase from the fused powders and an analysis of the mea sured Mossbauer spectra was used to determine the relative amounts of diffe rent phases in the powders. Raman spectroscopy together with X-ray diffract ion were also used for the structure characterization of the powders and fo r the identification of the two new undocumented compounds. The gas respons e properties of thick films made from the two "cleaned" new compound phases were studied at different temperatures between 100 degrees C and 400 degre es C. (C) 2000 Elsevier Science S.A. All rights reserved.