Fast proton conducting glasses: Creation by proton implantation and a requirement for fast proton conduction

Fast proton conducting glasses have been obtained in Mg(PO3)(2) glasses by implantation of protons at 120 keV to a fluence of 1X10(18) cm(-2). The de conductivity and the activation energy of the conduction in the implanted glasses are 5X10(-4) s cm(-1) at room temperature and 0.18 eV, respectively. No fast proton conduction was observed for H+-implanted SiO2 and Ca(PO3)(2) glasses. Infrared absorption spectra revealed that implanted protons are present in the form of X-OH (X = Si or P) in SiO2 and Ca(PO3)(2) glasses implanted with H+ ions to 1X10(18) cm(-2), but exist as POH groups and molecular water H2O in Mg(PO3)(2) glasses. A quantitative discussion on the proton conductivity led to the conclusion that the coexistence of acidic groups such as POH and molecular water H2O is a structural requirement for the emergence of fast proton conduction in oxide glasses. The formation of H2O in Mg(PO3)(2) was understood by considering its thermodynamic stability over SiO2 and Ca(PO3)2 glasses. (C) 1997 American Institute of Physics.