Fabrication of amorphous bulk and multi-phase ceramics by melting method in the HfO2-Al2O3-Gd2O3-Eu2O3system

Abstract

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 -Al 2 O 3 -Gd 2 O 3 system. The present study demonstrates the formation of the amorphous phases in quaternary systems HfO 2 -Al 2 O 3 -Gd 2 O 3 -Eu 2 O 3 . Furthermore, we have also succeeded to fabricate nanostructured bulk ceramics, which consisted of constituent oxide grains with 20-100 nm in size, by post annealing of the amorphous phase.

Fabrication of Nanocomposite Ceramics by Crystallization of Rapidly Solidified Eutectic Melts

“…Specific volume change during crystallization of the amorphous bulk by postannealing is shown in Fig. 9 (sample composition (mol%): HfO 2 / Al 2 O 3 / Gd 2 O 3 / Eu 2 O 3 = 14/ 63/ 18/ 5) 10 . Thermo dilatometory (TD) and differential thermal analysis (DTA) curves showed a correlation at the crystallization temperatures.…”

“… Differential thermal analysis and thermo dilatometory (TD) curves of HfO 2 –Al 2 O 3 –Gd 2 O 3 –Eu 2 O 3 amorphous sample with. TD dropped with crystallization due to reduced specific volume from the supercooled liquid to crystals 10 …”

Crystallization behavior of the eutectic glass in the C12A7–CaYAlO4 system

“…In the ternary eutectic system of HfO 2 -Al 2 O 3 -GdAlO 3 , we have also successfully fabricated an amorphous phase. 5,6 The calcium aluminate crystal, especially 12CaO·7Al 2 O 3 (C12A7), is also recently of great interest. C12A7 has been known as one component of alumina cement, but it has gathered attention due to several remarkable properties, i.e.…”