Boron anomaly in the thermal conductivity of lithium borate glasses

Abstract

Despite the importance of thermal conductivity for a range of modern glass applications, its compositional dependence and structural origins in modified oxide glasses remain poorly understood. In particular, the thermal conductivity of oxide glasses with network formers other than silica remain almost unexplored and no thorough connection with structural characteristics of glasses has been made. In this work, we study the thermal conductivity of binary lithium borate glasses using both experiments and classical molecular dynamics (MD) simulations. This glass system is chosen due to the nonmonotonic evolution in the boron coordination number as a function of composition and because glasses may be made in a wide compositional window. Specifically, we show that thermal conductivity exhibits a clear boron anomaly effect, as observed in both experiments and MD simulations. Thermal conduction is thus believed to mainly be promoted by the presence of fourfold coordinated boron. However, simulated vibrational density of states for the studied series suggests that the thermal conductivity is also influenced by the presence of the modifier ions based on an observed overlap between Li and O modes. Overall these results provide insights into the connection between thermal conductivity and structure of modified oxide glasses, which is the first step toward developing a model for predicting the composition dependence of thermal conductivity.

Predicting the dissolution rate of borosilicate glasses using QSPR analysis based on molecular dynamics simulations

“…One of the key structural features of borosilicate glass is the fraction of four‐fold coordinated boron (N 4 ) due to the boron anomaly phenomenon, greatly affecting glass properties 59–62 . Table 4 shows the percentages of N 4 values obtained from the Yun, Dell, Bray and Xiao (YDBX) model, 63,64 modified Bernstein model, 65 MD simulation, and experiment.…”

Phonon Sideband Analysis and Near-Infrared Emission in Heavy Metal Oxide Glasses

“…The structural mechanism responsible for the germanate anomaly well-known in the literature was proposed for glasses based on PbO-GeO 2 [14,15]. Similar to germanate glass systems, this anomalous composition dependence of physicochemical properties was also observed for borate-based glasses [16,17].…”

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

“…(A) Thermal conductivity ( κ ) and estimated diffusion contribution to thermal conductivity ( κ diff ) as a function of Li 2 O content in the studied x Li 2 O – (100 – x )GeO 2 system. (B) Correlation between the average speed of sound ( v s ) and κ for the studied glasses as well as a number of silicate (black) and borate (green) glasses 47,52–57 . Estimated errors are smaller than the size of the symbols.…”