Understanding phase equilibria in ceramic systems is central to the use and development of materials in refractories, glass, and other high-temperature technologies. Phase equilibria diagrams answer questions about flexibility and constraints of a ceramic or glass component in high-temperature or high-pressure environments. Phase boundaries also assist in the evaluation of the service stability of a ceramic material, both in the long and short time frames.  For an introdctory text on the use and interpretation of phase diagrams, please download General Discussions of Phase Diagrams by F.P. Hall, H. Insley, E.M. Levin, H.F. McMurdie and C.R. Robbins.