The structural relationships between the various phases of bismuth molybdates with special reference to their catalytic activity

Abstract

Including those reported here for the first time. there are at least seven distinct phases of bismuth molybdate: Bi₂O₃·nMoO₃, with n = 3, n = 2 and n = 1 (three variants); 3Bi₂O₃·2MoO₃; and 19Bi₂O₃·7MoO₃. Hitherto most of these phases have been interpreted to possess quite different, and seemingly unrelated, crystallographic structures. We advance arguments, based largely on high-resolution electron microscopy, as well as electron and X-ray diffraction studies. that the majority of these phases can be derived from the fluorite structure, a conclusion which offers new understanding and strategic scope in the design of new catalysts for the selective oxidation of hydrocarbons.