Investigations of structure and transport in lithium and silver borophosphate glasses

Glasses in the system xLi ₂O·(1- x)[0.5B ₂O ₃·0.5P ₂O ₅] and xAg ₂O·(1- x)[0.5B ₂O ₃·0.5P ₂O ₅] have been prepared from melt quenching method. Glasses have been characterized for their densities, molar volumes, glass transition temperatures and heat capacities. Structural studies have been done using infrared and high resolution magic angle spinning nuclear magnetic resonance (HR MAS NMR) of ³¹P, ¹¹B and ⁷Li nuclei. Boron is present only in tetrahedral coordination except in Li ₂O-rich glasses. Transport properties have been investigated over a wide range of frequency and temperature. Silver containing glasses are found to possess higher conductivities and lower barriers than lithium containing glasses. A structural model has been proposed in which pure B ₂O ₃-P ₂O ₅ compositions are assumed to be constituted of BPO ₄ units and modification occurs selectively on the phosphate moiety. Tetrahedral boron units are thus expected to be retained in the glass structure.