Ahmed Issa, Reiner Küchler, Rajan V. Anavekar, Roland Böhmer, Otmar Kanert, Himanshu Jain
December 4, 2009
Gold doped ruby glasses are classical examples of metal-glass nanocomposites that have been investigated for their striking optical properties. For their multifunctional applications, we have explored the nature of the electrical response of two oxide glasses containing a small amount (<0.1mol%) of gold. Gold-doped lithium borate (LBO) and lanthanum borogermanate (LBGO) glasses are studied using ac conductivity as a function of frequency and temperature in relation to their structure as determined by electron microscopy. For ionically conducting LBO, Au doping produces a noticeable increase of the electrical conductivity. For poorly conducting LBGO, gold doping introduces a dielectric loss peak indicative of dipolar relaxation. The heat treatment of both glasses introduces a new mechanism of dc conduction or dipolar loss, which has about one third the activation energy of the untreated samples. This unexpected behavior is attributed to an ionic-to-electronic conductivity transition in gold doped glasses.