Why not to search internet?
eg
http://en.wikipedia.org/wiki/Molybdenum(VI)_oxideSynthesis of β-MoO3 by Simple Evaporation of Molybdic Acid Solution Containing
Nitric Acid. — The title compound is synthesized by evaporation of a solution obtained
by cation exchange of an aqueous solution of Na2MoO4, after addition of HNO3
followed by heating at 573 K for 1 h in a stream of O2. The samples are characterized
by XRD, TG/DTA, and Raman spectroscopy. The role of ions in the selective formation
of β-MoO3 is discussed. — (MIZUSHIMA*, T.; FUKUSHIMA, K.; HUONG,
T. M.; OHKITA, H.; KAKUTA, N.; Chem. Lett. 34 (2005) 7, 986-987; Dep. Mater.
Sci., Toyohashi Univ. Technol., Toyohashi, Aichi 441, Japan; Eng.)