Effects of Li2O on Densification, Microstructure and Thermal Property of Spark Plasma Sintered AlN Ceramics

doi:10.3724/SP.J.1077.2011.00659

Abstract

Abstract: A newly developed rapid densify technique, spark plasma sintering (SPS), is used to prepare full-densified aluminum nitride (AlN) ceramics which are poorly sinterable. Some sintering aids are also used to promote the AlN ceramics’ densification and improve its thermal conductivity. In this work, effects of sintering aid Li₂O on densification, microstructure and thermal property of SPS sintered AlN ceramics were investigated. Results suggest that the initial sintering temperature of AlN samples reduce from 1550℃ to lower than 1200℃ with 1.0wt% Li₂O and 1.5wt% Sm₂O₃ (or Y₂O₃) adding as sintering aids . With Li₂O addition, AlN compacts can be fully densified at 1650℃. The microstructure of AlN compacts indicates that Li₂O is beneficial to generate aluminate liquid phase with better wettability and promote the densification of AlN ceramics, but it is unable to obtain higher relative density of AlN compacts because the escapement of gas phase though out liquid phase is very difficult in a rapid sintering process. Meanwhile, Li₂O addition affects the growth of AlN grains, and the better wettability of aluminate with AlN grain induces the homogeneous distribution of grain boundary phase. The deterioration of thermal conductivity of AlN ceramics is caused by the fact that the scattering of phonon is enhanced by small grain size and the secondary phase spreading adequately along the AlN grain boundaries. The thermal conductivity of AlN samples with 1.0wt% Li₂O and 1.5wt%Sm₂O₃ as sintering aids is lower than that of sample only with Sm₂O₃ as sintering aids.

Key words: sintering aids, aluminum nitride ceramic, spark plasma sintering, microstructure

CLC Number:

TQ174

LI Mei-Juan, SHEN Qiang, LUO Guo-Qiang, ZHANG Lian-Meng. Effects of Li2O on Densification, Microstructure and Thermal Property of Spark Plasma Sintered AlN Ceramics[J]. Journal of Inorganic Materials, 2011, 26(6): 659-663.

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