Towards routine refinement of hydrogenous materials by neutron powder diffraction

Paul Henry (ILL)

Traditionally, the collection of powder neutron data from hydrogenous materials has been considered largely fruitless due to the large, wavelength variable incoherent scattering contribution from hydrogen. This, coupled with relatively low neutron fluxes, has led to disproportionately long counting times for the quality of data collected. Practically, deuteration is often assumed to be a prerequisite for a powder neutron experiment. However, in many cases, deuteration profoundly changes the properties of the material under investigation, leads to the observation of completely different structures and/or phase behaviour or is impossible or incomplete making structural work impossible due to the negative / positive scattering lengths of H / D respectively. Materials of technological interest in the fuel cell, hydrogen storage, mineral and fast ion-conduction areas are currently hot topics in solid-state materials research. In these materials, the position of the hydrogen and its interaction with the host lattice are of utmost importance to understand the observed physical properties. As the majority of the host materials contain heavy atoms, locating the hydrogen positions and following their evolution using X-ray diffraction techniques, even using the high fluxes of a synchrotron source, is impossible. With the advent of very-high flux, variable resolution powder neutron diffractometers such as D20 at ILL, GEM and the upgraded HRPD and POLARIS diffractometers at ISIS, WOMBAT at Opal and POWGEN at SNS as well as planned new instruments worldwide, the feasibility of studying hydrogenous materials with powder neutron diffraction needs to be revisited. The power of the currently available instruments will be illustrated using a range of example materials from my ongoing collaborative research and instrumental development programme at ILL.

Back to Seminar Home Page

Last modified 12-May-2008 by website owner: NCNR (attn: )