Effects of rare-earth oxide and alumina additives on thermal conductivity of liquid-phase-sintered silicon carbide

• Published in: Journal of materials research Vol. 18; no. 8; pp. 1854 - 1862
• Main Authors: Zhou, You, Hirao, Kiyoshi, Yamauchi, Yukihiko, Kanzaki, Shuzo
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.08.2003
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.2003.0259

SiC ceramics were prepared from a β–SiC powder doped with two different sintering additives—a mixture of La2O3 and Y2O3 and a mixture of Al2O3 and Y2O3—by hot pressing and annealing. Their microstructures, phase compositions, lattice oxygen contents, and thermal conductivities were evaluated. The SiC doped with rare-earth oxides attained thermal conductivities in excess of 200 W/(m K); however, the SiC doped with additives containing alumina had thermal conductivities lower than 71 W/(m K). The high thermal conductivity of the rare-earth-oxide-doped SiC was attributed to the low oxygen content in SiC lattice, high SiC–SiC contiguity, and lack of β– to α–SiC polytypic transformation. The low thermal conductivity of the alumina-doped SiC was attributed to the point defects resulting from the dissolution of Al2O3 into SiC lattice and the occurrence of polytypic transformation.