Increased Thermal Conductivity of Liquid-Phase Sintering Silicon Carbide with Ytterbium Oxide and Magnesium Oxide

TL;DR

This paper shows that increasing the sintering temperature of silicon carbide with ytterbium and magnesium oxides boosts thermal conductivity by promoting larger grain growth.

Contribution

The study demonstrates a novel method to enhance thermal conductivity in SiC ceramics through controlled grain growth using specific sintering aids.

Findings

Thermal conductivity increased from 122.4 to 231.8 W/(m·K) as sintering temperature rose.

Grain size grew from 0.54 μm to 17.59 μm with higher sintering temperatures.

Larger grains reduced grain boundary density and interfacial thermal resistance.

Abstract

Using α-SiC powder as a raw material, with ytterbium oxide and magnesium oxide as liquid-phase sintering aids, silicon carbide ceramics were prepared via spark plasma sintering (SPS) at 1900, 2000, and 2050 °C with a 10 min dwell. As the sintering temperature increased, the grain size grew from 0.54 μm to 17.59 μm, while the thermal conductivity correspondingly increased from 122.4 W/(m·K) to 231.8 W/(m·K). Microstructural analyses revealed that elevated sintering temperatures significantly accelerated the dissolution–precipitation process, thereby inducing abnormal grain growth. Grain size is identified as the dominant factor governing the thermal conductivity of SiC ceramics. Larger grains reduce grain boundary density and interfacial thermal resistance, thereby facilitating phonon transport.

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