Cooling Rate Effects on Thermal Expansion of Sodium Alkaline‐Earth Aluminosilicate Glasses: Experiments and Simulations

ABSTRACT The coefficient of thermal expansion (CTE) is a critical property for oxide glass when used as a sealing material or carrier substrate, as matching the CTE with that of other materials is essential to prevent deformation, warping, and damage at the interface. The CTE is typically controlled by adjusting the glass composition; however, it is also influenced by the cooling rate during the production process. Nevertheless, the effect of cooling rate on the CTE of oxide glass materials has rarely been reported. In this study, the CTE and its dependence on cooling rate were experimentally investigated for a series of sodium aluminosilicate glasses with the composition (, Ca, Mg). The measurements were conducted at cooling rates of 1 and 100 K/min. Consequently, the effect of cooling rate was found to be more pronounced in ‐lean glasses, while it was insignificant for glasses with [] []. To elucidate the mechanism underlying the influence of content on the cooling rate dependence of the CTE, molecular dynamics (MD) simulations were conducted using two methods to estimate the CTE. The first method involved heating simulations to evaluate the volume change with temperature, while the second method measured fluctuations in enthalpy and volume to determine the CTE. The effect of cooling rate was investigated by performing MD simulations at four cooling rates: 0.1, 1, 10, and 100 K/ps, for two contrasting glass compositions, and , in . Consequently, the experimental trend—where the glass with is less sensitive to the cooling rate—was successfully reproduced by both methods when the glass structures were sufficiently equilibrated prior to measuring the CTE. Microstructure analyses revealed that doping stabilizes calcium coordination in the glass, thereby reducing the influence of cooling rate on the CTE. This may be attributed to the tendency of alkaline‐earth ions to localize around aluminum segregation.