Investigations of structure and transport in lithium and silver borophosphate glasses

Abstract

Glasses in the system xLi₂O.(1-x)[0.5B₂O₃.0.5P₂O₅] and xAg₂O.(1-x)[0.5B₂O₃.0.5P₂O₅] 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 Li₂O-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 B₂O₃-P₂O₅ compositions are assumed to be constituted of BPO₄ units and modification occurs selectively on the phosphate moiety. Tetrahedral boron units are thus expected to be retained in the glass structure.