β-MoO3 produced from a novel freeze drying route

Powdered samples of {beta}-MoO{sub 3} have been produced by the gentle heat treatment of freeze-dried molybdic acid at 350{degree}C for 1 hr. The samples, yellow-green in appearance, contained varying amounts of the thermodynamically stable {alpha}-MoO{sub 3}, depending upon the time and temperature of heat treatment. Neutron diffraction data were collected at 300 K. all peaks, not attributable to {alpha}-MoO{sub 3}, were indexed on the basis of a monoclinic cell, P2{sub 1}/c, {alpha} = 7.1228(7), b = 5.3660(6), c = 5.5665(6), {beta} = 92.01(1){degree}, V = 212.62(6){angstrom}{sup 3}. The structure, which is related to ReO{sub 3}, contains two crystallographically independent octahedra. Both show evidence of disorder at the Mo and O sites. Two distinct orientations of a short mo-O distance, suggestive of the type of molybdenyl bond observed in both the {alpha} and {beta}{prime}-forms, are primarily responsible for the observed disordering.