Synthesis and Characterization of Shaded Aluminum Nitride with the Addition of Transition Metal Oxides

Abstract

Aluminum nitride (AlN) powders were synthesized with 0.16-0.54mol% of transition metal oxides, such as TiO2, ZrO2, Nb2O5, MoO3, WO3, and Fe2O3, and characterized in terms of their powder's properties. The synthesized AlN powders were then sintered under N2 at 1850°C for 3h with 5mass% Y2O3 as a sintering aid. After which, the properties, such as density, thermal conductivity and optical transmittance, of the sintered ceramics were investigated. The chemical states in which the additives exist in both of the powders and the sintered ceramics were also investigated. Little change was observed in properties of the AlN powders when synthesized with the various additives, except for a small increase in oxygen content. The additives seem to change from being oxides to being nitrides during the synthesis process. A slight reduction in the thermal conductivity of the sintered AlN ceramics was noted with the addition of 0.16mol% of the additives, but this became large as the amount was increased to 0.54mol%. The additives in the sintered AlN ceramics existed as fine particles of either one of two kinds of chemical states; the elements of group IVa existed as nitrides while the others existed as metals. The sintered AlN ceramics with transition metal additives indicated low optical transmittance, particularly for those with MoO3 and Nb2O5. Consequently, shaded AlN ceramics with high thermal conductivity and virtually no optical transmittance in visible-light region were attainable.