Fabrication of amorphous bulk and multi-phase ceramics by melting method in the HfO₂-Al₂O₃-Gd₂O ₃-Eu₂O₃system

Ceramics have generally been fabricated from powders by shape forming & sintering methods except for glasses and glass ceramics. Glasses and glass ceramics can be fabricated by melting methods. The melting method has not only higher productivity but also higher shape forming ability than powder processes via forming & sintering methods. Thus we have reinvestigated melting methods in binary and ternary oxides systems to fabricate amorphous bulk ceramics and bulk nano composites. We have successfully fabricated amorphous phases by simple melt solidification methods in ternary eutectic melts in the HfO ₂-Al₂O₃-Gd₂O₃system. The present study demonstrates the formation of the amorphous phases in quaternary systems HfO₂-Al₂O₃-Gd₂O ₃-Eu₂O₃. Furthermore, we have also succeeded to fabricate nano-structured bulk ceramics, which consisted of constituent oxide grains with 20-100 nm in size, by post annealing of the amorphous phase.