The interaction between V-Sb or V-Cr-Sb oxides and alpha-Bi2Mo3O12 in mechanical mixtures during thermal treatments has been studied by laser Raman spectroscopy. Isolated V-Sb oxide and alpha-Bi2Mo3O12 remain unchanged up to above 600 degrees C. When mixed, V-related bands start to disappear and Bi-Mo-related bands widen already at 600 degrees C indicating some kind of interaction between them. The presence of Cr2O3 in the mixture speed up this interaction, leading to the formation of a new Bi-Mo-V-O compound at temperatures below 600 degrees C.