Attempt to fabricate a high thermal conductivity, transparent oxide glass by dispersing MgO crystals and refractive index matching

Nobuaki Terakado,Toshikazu Yoshimine,Yoshihiro Takahashi,Takumi Fujiwara,Ryusei Kozawa

doi:10.1063/1.5054339

Abstract

Oxide glasses generally have low thermal conductivity due to their disordered structures. Here, a fabrication method to provide them with high thermal conductivity while retaining their optical transparency is proposed. It consists of dispersing ∼20 μm MgO crystals in a glass matrix and matching their refractive indexes to prevent the decrease of the oxide glass optical transparency due to light scattering. The dispersion of the MgO crystals increased the thermal conductivity of the original glass by ∼50% and the new glass still exhibited optical transparency. Such MgO-dispersed glass could be successfully used in thermal management applications requiring both transparency and formability.

Highlights

Various heat dissipation materials have been recently developed in the electronics field due to the rapid increase of heat density in highly powered and integrated electronic devices.[1,2,3] Such materials do not include oxide glasses because of their low thermal conductivity, considerably smaller than that of the corresponding crystals, for example SiO2 (i.e., ∼1.4 W/(m·K) for the glass, ∼12 (||c) and ∼7 W/(m·K) (⊥c) for the quartz, at room temperature).[4,5] This is because propagation of atomic vibration which is the origin of heat transfer of glasses is disturbed by the huge amounts of scattering centers originated from the intrinsic structures of oxide glasses.[4]
Providing them with high thermal conductivity could pave the road for new heat dissipation applications, e.g., as encapsulation materials for high-power lighting devices including ultraviolet–light-emitting diodes (UV-LEDs) and building materials such as windows, where their properties are strongly favorable
We propose to overcome this manufacturing challenge by the dispersion of high thermal conductivity crystals into a glass matrix and their refractive index matching to retain the original optical transparency

Summary

Introduction

Various heat dissipation materials have been recently developed in the electronics field due to the rapid increase of heat density in highly powered and integrated electronic devices.[1,2,3] Such materials do not include oxide glasses because of their low thermal conductivity, considerably smaller than that of the corresponding crystals, for example SiO2 (i.e., ∼1.4 W/(m·K) for the glass, ∼12 (||c) and ∼7 W/(m·K) (⊥c) for the quartz, at room temperature).[4,5] This is because propagation of atomic vibration which is the origin of heat transfer of glasses is disturbed by the huge amounts of scattering centers originated from the intrinsic structures (e.g., disordered atomic network and defects) of oxide glasses.[4]. We propose to overcome this manufacturing challenge by the dispersion of high thermal conductivity crystals into a glass matrix and their refractive index matching to retain the original optical transparency. When both dispersed crystals and glass matrix are optically transparent, as in the present study, light scattering at the interface between the two phases causes opacity.

Results

Conclusion