1Processing and Application of Ceramics 4 [1] (2010) 1–6 Composite material in the Al2O3-20 vol % YAG system#

Within alumina particle suspension yttria precursor was precipitated with ammonium carbonate. Drying and calcination at 600°C resulted in the mixture of alumina and yttria particles, the latter being much finer than alumina particles. This mixture was additionally homogenized by short attrition milling in aqueous suspension of pH selected on the basis of zeta (ζ) potential measurements. It was found that acidic conditions (realized with HNO3) resulted in hard agglomerates. Such powder shows poor sintering ability. Much better properties showed powders homogenized under basic conditions. They give dense materials composed of YAG inclusions within alumina matrix. YAG particles resulted from the reaction of Y2O3 with Al2O3 during heat treatment. Ho-mogenization of the system mixed at pH=8, corresponding to the heterofloculation conditions, is slightly better than observed at pH=10. YAG inclusions (20 vol%) increase hardness and fracture toughness of the material in comparison with pure alumina polycrystals