X-RAY-DIFFRACTION ANALYSIS

X-ray diffraction analyses were carried out by nine laboratories. The equipment and experimental conditions of analysis were generally diffe rent. However, the results obtained were very similar and coherent. Sa mples with a high vanadium content showed exclusively the presence of TiO2 (anatase) and crystallites of V2O5 as long as not pretreated. No TiO2 (rutile) or other vanadium oxide was observed. V2O5 was also obse rved in low vanadium content samples in two analyses. No other crystal line phases could be observed, although the presence of very weak line s were detected. These lines were not identified as vanadium oxide, ti tanium oxide or vanadium-titanium oxide. In the pretreated samples con taining vanadium, the presence of V2O5 lowered the temperature of the phase transition of anatase to rutile.