Low Temperature Sintered AlN Ceramics and Characteristic of Mechanical Property and Thermal Conductivity

Abstract

The high thermal conductivity and low electrical conductivity, coupled with its nontoxic nature, make AlN ceramics the best materials for the insulating substrate applications. It is recently important issue to make the high strength of AlN ceramics in an appropriate levels as well as thermal conductivity. Normally, AlN has been densified at high temperature. However, the high sintering temperature not only increases the production cost of AlN but also causes significant grain growth, which results in a reduction of mechanical strength. In this regard,the research on AlN ceramics has been mainly focused on attaining full densification at low sintering temperature with various sintering additives. In this study, effects of multiple additives on the low temperature sintering of AlN were examined. The additives not only form a liquid phase to enhance densification, but improve the thermal conductivity by elimination the oxygen from the AlN lattice. Thermal conductivity was characterized by laser flash method and Raman spectroscopy. With Raman, the relative amount of oxygen in AlN lattice can be calculated. Moreover, high mechanical strength of AlN was obtained by suppressing the grain growth which results from lowering sintering temperature.