Ceramics-Silikáty 55 (3) 208-213 (2011)

Composites with eutectic microstructure by hot pressing of Al₂O₃–Y₂O₃ glass microspheres

A. Prnová, D. Galusek, M. Hnatko, J. Kozánková, I. Vávra

In the work we describe the use of Al₂O₃–Y₂O₃ glass microspheres with high alumina contents prepared by flame synthesis as a precursor for materials with binary eutectic microstructure and high hardness. XRD amorphous microspheres with eutectic composition in a pseudobinary system Al₂O₃–Y₃Al₅O₁₂ (YAG) were prepared by feeding a crystalline powder precursor of respective composition into methane-oxygen flame. The microspheres with the mean diameter ≈10 μm were hot-pressed in vacuum under various conditions (temperatures 840-1600°C, pressure 30 or 40 MPa, isothermal dwell 0-120 min). Hot pressing at 1600 °C without isothermal dwell yielded fully dense bulk materials with fine two phase microstructure with Al₂O₃ and YAG phases percolating at submicrometre level and with hardness 15 GPa. Extension of the isothermal dwell resulted in undesirable coarsening of the resulting microstructure.

 Keywords: Al₂O₃–Y₂O₃ glass microspheres, Hot pressing, Eutectic microstructure