Microstructural development of a P2O5-modified cordierite glass ceramic during sintering Part 1. Microscopic characterization

Abstract

The crystallization sequence of a P2O5-modified cordierite glass was investigated using conventional and analytical transmission electron microscopy, as well as transmission optical microscopy. The experiments show surface nucleation for both bulk and powdered glass specimens. The crystallization process leads to a preferred orientation of high-cordierite crystals via a metastable high-quartz solid solution. The hexagonal crystal lamellaes grow with their c axis perpendicular to the surface. A distinct dependence of the cordierite lamellae size on the crystallization temperature is observed. The residual glassy phase between the cordierite lamellae develops via a phase-separation process into a SiO2-rich amorphous phase and a polycrystalline matrix with magnesium orthophosphate as the major phase.