Hydration process of β-MoO3 powder prepared by pulsed wire discharge method

The hydration of β-MoO3 and α-MoO3 powders was investigated through powder exposure experiments at 24 ℃ in the air with a relative humidity of 53%. X-ray diffraction results showed a hydrated phase of MoO3·0.34H2O in only exposed β-MoO3 powder, while the α-MoO3 powder maintained its initial phase. By thermogravimetry-differential thermal analysis and mass spectrometry measurements and the dehydration experiments, the stable temperature range of the hydrated phase made by β-MoO3 was identified below 285 °C, and above this temperature, the hydrated phase transformed back to the original β-MoO3 phase. The other analysis methods using field-emission scanning electron microscopy and field-emission transmission electron microscopy were also used to determine powders’ morphology and size and to confirm phases from their lattice images. To the best of our knowledge, this is the first report on the formation of the hydrated phase by exposing β-MoO3 powder in the humid air.