In situ study of the formation of crystalline bismuth molybdate materials under hydrothermal conditions

The three well-known and catalytically important phases of bismuth molybdate have been prepared, in a phase pure form, employing hydrothermal methods at temperatures below 200 degreesC. An in situ study of the formation of these phases using the time-resolved energy-dispersive X-ray diffraction (EDXRD) technique revealed that the a and gamma crystalline phases are formed directly from the amorphous gel mixture without forming any intermediate phases. Kinetic data analysis using the Avrami-Erofe'ev nucleation-growth model suggests that the mechanisms for formation are different for each phase. This hydrothermal method of preparation yielded materials with a higher surface area as compared to the solids prepared by conventional techniques.