High-temperature incommensurate-to-commensurate phase transition in the Bi2MoO6 catalyst

The temperature-dependent behavior of the low- and intermediate-temperature phases of gamma -Bi2MoO6 were investigated, As revealed by high-resolution neutron and synchrotron powder diffraction as well as electron diffraction, the low-temperature Aurivillius phase shows a previously undetected incommensurate modulation: along the pseudo-tetragonal a (q(a) = 0.5626(2)) and c (q(c) = 0.2844(2)) axes, A reversible incommensurate-to-commensurate phase transition to the intermediate-temperature phase occurs near 840 K, before irreversibly transforming near 880 K into the fluorite-related high-temperature polymorph described in detail by two of us in an earlier study (Buttrey et al,, J, Solid State Chem. 111, 118-127 (1994)), (C) 2000 Academic Press.