Transition metal ion-containing glasses and glass-ceramics are of interest owing to their combined ferroelectric, optical and electrical properties. For example, alkali niobium silicate glasses offer tailorable physical properties and crystallization behavior, but limited attention has been given to the overall glass-forming regions (GFR) in the Rb 2 O-Nb 2 O 5 -SiO 2 ternary system. In this report, we explore the GFR extending up to 30 mol% of Nb 2 O 5 , 65 mol% of Rb 2 O. The glasses consist of interwoven networks of niobate and silicate units, generating a highly inverted state when approaching the upper limits of Rb 2 O content. While Nb 2 O 5 promotes high packing density and volume density of energy, increasing Rb 2 O content reduces network crosslinking and thus decreases network dimensionality. Hence, by appropriately defining the Nb 2 O 5 /Rb 2 O ratio - and therefore the mobility and concentration of charge carriers - a substantial enhancement in electrical conductivity can be achieved with only a moderate decrease of the elastic modulus.
Sun et al. (Sat,) studied this question.