The formation of crystalline gamma-Bi2MoO6 during hydrothermal synthesis was followed by a combination of HRPD XANES and Raman scattering in situ techniques The environment of Mo species changes from isolated tetrahedral MoO42- in the initial gel to distorted octahedra in gamma-Bi2MoO6 (Raman XANES) In the initial stages spherical (Bi Mo)(2)O-3 particles form with a fluorite structure and the growth of anisotropic platelets of gamma-Bi2MoO6 follows in a second step (HRPD) The presence of molybdenum specie in the intermediate (Bi Mo)(2)O-3 mixed oxide was ascertained by EDS during complementary ex situ experiments These particles are assumed to be involved in the crystal growth process their structure acting as a skeleton for the formation of gamma-Bi2MoO6 koechlinite (C) 2010 Elsevier B V All rights reserved