Analysis of the cordierite X-phase and phase transformation by electron backscatter diffraction (EBSD)

The cordierite system has been the main model system for research concerning the nucleation and surface crystallization in glasses for many years. Previous results gained by applying electron backscatter diffraction (EBSD) to this system are also valid for samples of the reference melt (GM 30870, provided by the SCHOTT AG) which has served as a reference glass for many articles published by researchers around the world. EBSD-patterns for the X-phase, one of the remaining mysteries in the system, are presented. Our results also indicate that the X-phase nucleates after the cordierite crystals have already grown to a solid layer at the surface. Further results indicate a phase transition from the metastable μ-cordierite to thermodynamically stable indialite along the grain boundaries of samples stored for 15 years after crystallization in a normal atmosphere.