High pressure resonant X-ray emission studies of WO₃ and hydrogenated WO₃

Abstract

We performed two high pressure resonant x-ray emission experiments (RXES) on tungsten oxide (WO3), and a mixture of WO3 and ammonia borane (NH3BH3), respectively. In the first experiment, WO3 (confined by a Be gasket) was pressurized and RXES spectra were collected from ambient pressure up to 54.8 GPa via incident x-ray excitation of the W LIII line at 10.207 keV and collection of emission spectra from the Lα1 line near 8.398 keV. The spectra display significant alterations, in particular, a diminishment of one of the spectral lines with pressure suggesting some electronic state changes with pressure in WO3 which were largely reversible upon decompression of the sample to ambient pressure. For the second experiment, a powder mixture of WO3 and NH3BH3 was pressurized and irradiated to release H2. An RXES pattern was recorded at 4 GPa which displayed little difference between the RXES spectrum recorded of pure WO3 in the first experiment. However, at 10 GPa, a dramatic change occurred in the RXES spectrum suggesting that the H2 reacted with and/or intercalated into the WO3 lattice. These studies suggest the possibility of harnessing useful hard x-ray photochemistry as a novel means to dope semiconductors.

Measurement of the Energy and High-Pressure Dependence of X-ray-Induced Decomposition of Crystalline Strontium Oxalate

“…Advances have been made in the field of useful hard X-ray photochemistry to synthesize novel compounds such as CsF 2 , CsF 3 , and OF 2 , , to dope semiconductors such as WO 3 , and to create a form of novel doped polymeric carbon monoxide . In all cases, the highly ionizing, highly penetrating, and highly focused properties of hard X-rays (>7 keV) are harnessed to initiate decomposition and synthesis under extreme or ambient conditions.…”

Cationic Dependence of X-ray Induced Damage in Strontium and Barium Nitrate

“…Moreover, X-rays can be harnessed to produce simple molecules such as Cl 2 , O 2 , and even F 2 , , in situ inside diamond anvil cells (DACs) for study at high pressure and to serve as reactants for further chemical reactions. X-rays have also been employed to dope semiconductors such as WO 3 …”