Hydrogen-enhanced electrical conductivity of diopside crystals

Dehydration and electrical conductivity (sigma) experiments were performed on diopsides from India (In), Sri Lanka (Sri) and Russia (Ru) to study the effect of hydrogen (H) on sigma. Dehydration showed that hydrogen concentra tions (CH) of In- and Sri-diopsides remained constant (similar to 50 and si milar to 900 H/10(6) Si), and C-H in Ru-diopside decreased continuously fro m 1000 to 100 H/10(6) Si within 72 h. sigma's were measured at T=1193-1473 K, P=0.1 MPa and f(O2)=10(-9) MPa. Different changes in sigma with time wer e observed: the sigma of Ru-diopside was reduced by one order of magnitude within 72 h as crystals dehydrated; sigma s of In- and Sri-diopsides remain ed time-independent. Sri-diopside shows the highest sigma corresponding to its highest C-H among the three crystals. Our results suggest an important effect of H on the sigma of diopsides. We interpret this as a result from t he fast diffusion of H incorporated into diopside. Also the concentration a nd mobility of intrinsic charged defects may increase due to the presence o f H.