Crystallization mechanism of Na2O-CaO-Al2O3-SiO2-F- class containing Cr2O3

The effect of Cr2O3 On the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specrometer) and so on. Computer pattern recognition is applied to optimize the heat-treatment schedules. The experimental results show that the base glass containing more than 1.5 % (mass fraction) Cr,Ol can be nucleated internally and converted to spheroidal crystal glass materials. The spheroidal crystal consisted of fibrous wollastonite crystals radiating from a center. The residual glass phase filled in the interstices between the fibers and between the spherulites. During heat treatment process, the valence states of chromium changed from Cr6- to Cr3+, and the Cr-spinet solid solution [CaCr2O4] precipitated followed this valence change. At the primary stage of crystallization, the Cr-spinel could act as a nucleating center on which the principal crystalline phase beta-CaSiO3, grew epitaxially.