Structural origin of electrical conductivity of copper lithium metaphosphate glasses

Abstract We have sought the structural origin of the recently reported electrical conductivity of lithium copper phosphate glass system (50-x) Li 2 O-xCu 2 O-50 P 2 O 5 , as lithium oxide is gradually replaced by Cu 2 O. The structure of these glasses was determined by X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy and Raman spectroscopy. The results show the presence of both mobile Cu + and relatively immobile Cu 2+ ions. The relative fraction of Cu 2+ [Cu 2+ / Cu tot ] and non-bridging oxygen increases with x; the latter indicating a tendency towards depolymerization of the network. On the other hand, there is enhanced crosslinking within the network as P O ⋯ Li bonds are replaced by relatively covalent P O ⋯ Cu bonds. This leads to a more cross-linked structure and a progressive reduction of the optimum sites for the jumping of both Li + and Cu + , in agreement with the observed increase of the energy barrier for ion transport as Li 2 O is replaced by Cu 2 O.