Electrical properties of Li2O-La2O3-SiO2 electrode glasses after Ta2O5 doping and Ta implantation

Electrical conductivities, sigma, of the Li2O-La2O3-SiO2 glasses were investigated as functions of Ta2O5 doping and Ta ion-implantation. A linear relationship between logarithm sigma and the inverse of the sample temperature, T, was found in 2 to 4 mol% Ta2O5 doped Li2O-La2O3-SiO2 glasses. The conductivity increases as Ta2O5 content increases at sample temperatures above 100 degrees C. Fluences of 50 keV Ta ions per cm(2) from 5 x 10(16) to 2 x 10(17) were implanted into 0% and 2% Ta2O5; containing Li2O-La2O3-SiO2 glass samples. The activation energy of the conductivity was deduced from the relation between log sigma and 1/T. It was found in implanted samples that the conductivity increased, but the activation energy and Tk-100 decreased, where Tk-100 is the sample temperature when the conductivity reaches 100 x 10(-1) S/cm. However, the Ta2O5 containing implanted samples show higher conductivities, lower activation energies and lower Tk-100. X-ray photoelectron spectroscopy (XPS) was used to study the structural modification introduced by implantation. Bridging oxygen (BO) and non-bridging oxygen (NBO), were observed in all samples. The changes in relative concentrations of BO and NBO before and after implantation clearly indicate the structure modification which results in the increase of the conductivity. It was clearly demonstrated in this study that both doping Ta2O5 and implanting Ta ions enhance the conductivity of Li2O-La2O3-SiO2 electrode glasses. (C) 2000 Kluwer Academic Publishers.