Thermal behaviour of WO3 and WO3/TiO2 materials

The knowledge of the interdependence between the structural, thermal and el ectric properties of oxide semiconductors contributes to widen their practi cal application. In this work the thermal behaviour of WO3 and WO3/TiO2 pow ders and thick films - studied by DSC - is compared with the results of X-r ay diffraction (XRD) investigation in the temperature range 25-500 degreesC . The X-ray analyses show a reversible phase transition (from gamma -WO3 in to beta -WO3) both in WO3 and in WO3/TiO2. However, while in the WO3 the tr ansition takes place between 300 and 400 degreesC, in the WO3/TiO2 system i t is not complete even at 400 degreesC, during the measurement time. The ph ase transition in the WO3 was identified between 320 and 360 degreesC also by DSC, but in the bicomponent material no sharp transition could be detect ed. This may mean that titanium can thermally stabilize the WO3, influencin g also its electric properties. (C) 2001 Elsevier Science B.V. All rights r eserved.