The mechanism of crystallization from a B2O3-containing glass, with composition based in the CaO–MgO–Al2O3–SiO2 system, to a
glass–ceramic glaze was studied by different techniques. Glass powder pellets were fast heated, simulating current industrial tile processing
methods, at several temperatures from 700 to 1200 C with a 5 min hold. Microstructural study by field emission scanning electron
microscopy revealed that a phase separation phenomenon occurred in the glass, which promoted the onset of mullite crystallization at
900 C. The amount of mullite in the glass heated between 1100 and 1200 C was around 20 wt%, as determined by Rietveld refinement.
The microstructure of the glass–ceramic glaze heated at 1160 C consisted of interlocked, well-shaped, acicular mullite crystals longer
than 4 lm, immersed in a residual glassy phase.
2006 Elsevier B.V. All rights reserved.
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