Ion-exchange loading of yttrium acetate as a sintering aid on aluminum nitride powder via aqueous processing

A novel fabrication profess of AlN ceramics via aqueous colloidal processin g and pressureless sintering has been presented. The chemical stability of AlN powder in water was improved by the surface chemical modification with sebacic acid, while maintaining a hydrophilic surface. The treatment of the sebacic acid-modified powder with yttrium acetate tetrahydrate resulted in strong immobilization of Y3+ ions, as a sintering aid, at a highly dispers ive level on the AlN powder surface through ion exchange with the free carb oxyl groups of the sebacic acid molecules attached to the AlN surface. By s electing slip compositions for a well-deflocculated condition and firing co nditions to burn out organic components in the slip cast compacts, a therma l conductivity of about 250 W/(m.K) could be attained by the pressureless s intering at 1900 degreesC for 5 h.