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RESEARCH PRODUCT

Microstructural Evolution in Fast-Heated Cordierite-Based Glass-Ceramic Glazes for Ceramic Tile

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The crystallization mechanism of α-cordierite from a B 2 O 3 -and TiO 2 -containing glass submitted to fast heating in the cordierite primary phase field of the CaO-MgO-Al 2 O 3 -SiO 2 quaternary system was investigated. Addition of B 2 O 3 to a SiO 2 -rich glass suppressed the formation of μ-cordierite. This suppression facilitated densification by viscous flow before crystallization. Powder X-ray diffractometry, field-emission electron scanning microscopy, and energy-dispersive X-ray analysis revealed that α-cordierite nucleated directly from glass on the boundaries of original particles and was probably favored by TiO 2 , which acted as a nucleant. The growth kinetics of α-cordierite crystals was fast, and the crystals seemed to grow by consuming glass directly from the growing interphase. The estimated amount of α-cordierite in the glass heated at 1160°C was 69.5 wt%, as determined using the Alegre method. The final microstructure consisted of an arrangement of well-shaped hexagonal prisms, with sizes <3 μm, immersed in a residual glassy phase. The feasibility to develop new glass-ceramic glazes using the present and previous works is considered.