Hydrogen tracer diffusion in LiBH(4) measured by spatially resolved Raman spectroscopy

The hydrogen tracer diffusion in LiBH4 has been determined by spatially resolved Raman spectroscopy. The measurements give direct evidence of a macroscopic diffusion of BH-4 ions as well as atomic exchange of hydrogen between the anions. An effective tracer diffusion coefficient of deuterium in LiBH4 of D ≃ 7 × 10-14m2 s -1 at 473 K is derived. The direct exchange rate of hydrogen between BH4 units is 10 orders of magnitude slower, i.e. the relatively fast effective hydrogen diffusion has its origin in the fast diffusion of BH 4 units. © 2010 The Owner Societies