Glass can keep a drink safely contained, protect a smartphone screen, or serve as a foundation for electronic components. But when it comes to controlling heat, this familiar material still holds some scientific mysteries. Now, researchers have identified a key factor governing how efficiently heat travels through silicate glass, offering a new guideline for designing glass materials for next-generation electronic devices.
A research team led by Tohoku University investigated 13 different silicate glass compositions to understand how their thermal properties influence heat conduction. Their findings revealed that the speed of sound through glass plays the dominant role in determining its thermal conductivity.
“Thermal conductivity has been studied for a long time, yet it remains one of the least understood properties of non-crystalline materials,” says Sohei Sukenaga, associate professor at Tohoku University. “Our findings provide a clearer guideline for designing the thermal conductivity of glass, which could help researchers develop materials suited to the thermal demands of next-generation electronic devices.”
Thermal conductivity describes how easily heat travels through a material. It is an important property in applications ranging from smartphone displays to electronic components, where controlling heat can affect performance and reliability. Glass can also be used as a thermal insulator, making it important to understand what determines whether heat moves through it easily or slowly.
However, measuring thermal conductivity can be time-consuming, and experimental data for glass materials remain limited. Scientists have known that thermal conductivity is related to three factors: how much heat a material stores, how quickly sound waves travel through it, and how far tiny vibrations can travel before being scattered. These vibrations are carried by quasiparticles called phonons, which play a central role in heat transfer through insulating materials.
What remained unclear was how these factors interacted with one another and which should be prioritized when designing glass compositions with specific thermal properties.
To investigate, the team measured thermal conductivity, sound velocity, volumetric specific heat and phonon mean free path in 13 silicate glass compositions at room temperature. Volumetric specific heat indicates how much energy a given volume of glass can store as its temperature rises, while the phonon mean free path describes the average distance a phonon travels before being scattered.
Copyright: ©Sohei Sukenaga et al.
The results revealed a trade-off between volumetric specific heat and phonon mean free path: as one increased, the other tended to decrease. Their product remained approximately constant across the glass compositions studied. In contrast, thermal conductivity was found to be proportional to sound velocity, identifying it as the dominant factor governing heat conduction in these materials.
This relationship offers a practical direction for glass design. Rather than treating several thermal parameters as independent variables, researchers may be able to focus on controlling sound velocity when developing silicate glasses with desired thermal conductivity. Such an approach could help guide the development of glass materials for future electronic devices, where effective heat management is increasingly important.
The next step is to determine whether this relationship also applies to other types of materials and whether it holds at temperatures beyond room temperature. If confirmed, the findings could provide a broader foundation for understanding and designing the thermal properties of non-crystalline materials.
The study, “Dominant role of sound velocity in the thermal conductivity of silicate glasses,” by Sohei Sukenaga, Bunta Ozato and Hiroyuki Shibata, was published in Applied Physics Letters. The paper was selected as a Featured Article and highlighted in the journal’s Scilight research summary.
- Publication Details:
Title: Dominant role of sound velocity in the thermal conductivity of silicate glasses
Authors: Sohei Sukenaga, Bunta Ozato, Hiroyuki Shibata
Journal: Applied Physics Letters
DOI: 10.1063/5.0351403
