Oxide/oxide composites in the system Cr2O3-Y2O3-Al2O3

Ceramic compacts in the systems Al2O3-Y2O3, Cr2O3-Y2O3 and Y-3(CryAl1-y)(5) O-12 (Cr-doped YAG) were prepared by solid state reaction in calcined co-pr ecipitated powder mixtures of appropriate compositions. Various solid-solut ion phases were formed, e.g. Y-3(Al1-xCrx)(5)O-12, YAlyCr1-yO3 and Al2-xCrx O3. Composite materials in the pseudo-binary or ternary systems Al2O3 - Y3A l5O12, Cr2O3 - Y2O3 and Y-3(Al1-xCrx)(5)O-12-YAlyCr1-yO3-(AlzCr1-z)(2)O-3 w ere obtained by hot-pressing appropriate powder precursors at 1600-1650 deg rees C for 1 h. The microstructure of the prepared materials was studied in a scanning electron microscope with element analysis facilities. X-ray dif fraction was used to reveal the phases present and their lattice parameters . The chemical compatibility of these phases was investigated. The results are discussed with a special emphasis on the solubility of Cr in the YAG st ructure, and on the compatibility relationship between Cr-doped YAG and its neighbouring phases. A gel-coating process for preparing Al2O3-YAG composi tes with tailored microstructures is also described. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.