HIP焼結した窒化ケイ素の熱係数の温度依存性

抄録

Thermal diffusivity and conductivity as well as specific heat of capsule-HIPped Si₃N₄ with Y₂O₃ and Al₂O₃ 6mol% in total as additives were measured at different temperatures ranging from 100 to 1300K. The isobaric specific heat C_p agreed with the isochoric specific heat C_v calculated by the Debye's theory, assuming that silicon and nitrogen atoms are lattice dynamically equivalent. The Dulong-Petit's rule applied well to sintered Si₃N₄ at high temperatures and C_v≅25J/(K·mol). The glassy phase quantity could be estimated by the difference of the measured specific heat and the calculated specific heat at low temperatures. The specimens with higher thermal diffusivity and conductivity at low temperatures were those with higher β-phase fraction, larger particle size of raw Si₃N₄ and richer Y₂O₃ additive. For these specimens the thermal diffusivity and conductivity showed a larger temperature depencence.