Process for preparation of dense molded bodies of polycrystalline aluminum nitride without use of sintering aids

Abstract

Abstract The invention is a molded body of polycrystalline aluminum nitride having a density of at least 99.8% TD and comprising: ______________________________________ at least 99 % by weight A1N up to 0.35 % by weight residual oxygen up to 0.35 % by weight residual carbon and up to 0.30 % by weight metallic impurities (Fe, Si, Ca, Mg). ______________________________________ In the molded body, the aluminum nitride is present in the form of a single phase, homogeneous, isotropic microstructure having a maximum grain size of 5 μm. The residual oxygen and the residual carbon are present in the form of a solid solution in the aluminum nitride lattice and ceramografically not detectable as separate phase(s) up to a manification of 2400 times. The molded bodies have a bending strength measured according to the 4-point method, at room temperature and up to about 1400° C., of at least 500 N/mm 2 , a predominantly transcrystalline rupture modulus and a thermal conductivity at 300 K of at least 150 W/mK. The molded body is produced from a porous, deoxidized green body having a maximum density of 70% TD and the same chemical composition as the final product, by isostatic hot pressing in a vacuum sealed casing at a temperature of from 1700° to 2100° C. and a pressure of from 100 to 400 MPa in a high-pressure zone using an inert gas as a pressure transmitting agent.

Inventors

• 👤 Karl-Alexander Schwetz
• 👤 Wolfgang Grellner
• 👤 Klaus Hunold
• 👤 Max Mohr
• 👤 Alfred Lipp

Bibliographic Details