Ceramic compacts in the systems Al 2 O 3 -Y 2 O 3 , Cr 2 O 3 -Y 2 O 3 and Y 3 (Cr y Al 1 - y ) 5 O 1 2 (Cr-doped YAG) were prepared by solid state reaction in calcined co-precipitated powder mixtures of appropriate compositions. Various solid-solution phases were formed, e.g. Y 3 (Al 1 - x Cr x ) 5 O 1 2 , YAl y Cr 1 - y O 3 and Al 2 - x Cr x O 3 . Composite materials in the pseudo-binary or ternary systems Al 2 O 3 -Y 3 Al 5 O 1 2 , Cr 2 O 3 -Y 2 O 3 and Y 3 (Al 1 - x Cr x ) 5 O 1 2 -YAl y Cr 1 - y O 3 -(Al z Cr 1 - z ) 2 O 3 were obtained by hot-pressing appropriate powder precursors at 1600-1650 o C for 1 h. The microstructure of the prepared materials was studied in a scanning electron microscope with element analysis facilities. X-ray diffraction 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 structure, and on the compatibility relationship between Cr-doped YAG and its neighbouring phases. A gel-coating process for preparing Al 2 O 3 -YAG composites with tailored microstructures is also described.