Study of the Melting Behavior of YAG Single Crystal by Optical Differential Thermal Analysis
Abstract
The melting point of yttrium aluminum garnet (YAG), reinvestigated by optical differential thermal analysis (ODTA), was found to be 1940 + or - 7 C. Above this temperature YAG liquids are opaque, suggesting the presence of two immiscible liquids. In the composition range 10.0 to 47.5 mol. % Y2O3, crystallization of the equilibrium phases can only occur in the presence of YAG nuclei; otherwise solidification of YAlO3 and Al2O3 will take place. A metastable phase diagram has been defined with a metastable eutectic at 23 mol. % Y2O3 - 77 mol. % Al2O3 and 1702 + or - 7 C. YAlO3 (perovskite) was found to melt incongruently with a peritectic temperature of 1916 + or - 7 C and a liquidus temperature of 1934 + or - 7 C. YAlO3 formed during metastable solidification transforms to YAG in the presence of Al2O3 at 1418 + or - 7 C. It is suggested that the metastability arises from the difficulty of the aluminum to attain fourfold coordination in the YAG structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1979
- Accession Number
- ADA080049
Entities
People
- Dennis J. Viechnicki
- Jaroslav L. Caslavsky
Organizations
- United States Army Research Laboratory