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1770824 
Journal Article 
Vitrification and devitrification phenomena in the ternary MgO-Al2O3-B2O3 system 
Hamzawy, EMA; Darwish, H 
2008 
1 
Ceramics International
ISSN: 0272-8842
EISSN: 1873-3956 
34 
8 
1965-1969 
WOS:000260735500025 
The ternary MgO-Al2O3-B2O3 system was studied with respect
to the final product that either amorphous or devitrified glasses in the down middle region of
the phase diagram. The developed phases in either the devitrified or the crystallized glasses
were investigated. Magnesium borate (Mg2B2O5) and a spinel (MgAl2O4) phases were developed in the
devitrified samples during the cooling of the melts, whereas the crystallization of the formed
glasses led to the development of magnesium berate (e.g. suanite (Mg2B2O5) and kotoite (Mg3B2O6))
and aluminium borate (Al4B2O9) phases. The microstructures of the studied crystalline glasses
were characterized by volume crystallization of either lath- or rounded-like crystals of suanite
and Al-borate phases. The grain size of the formed crystals were increased from 10 mu m to 500 nm
with the domination of suanite or Al-borate phases. The coefficient of thermal expansion (CTE)
changed from 69 to 59 x 10(-7)degrees C-1 for glasses and from 81 to 56 x 10-7 degrees C-1 for
the glass-ceramics, in the 20-500 degrees C range. The data of the glasses were correlated to the
local structure changed induced by increasing of Al2O3/MgO and MgO/B2O3 ratios. The results of
the glass-ceramics were explained on the basis of the nature and concentration of all phases
formed including a residual glassy matrix. (C) 2007 Published by Elsevier Ltd and Techna Group
S.r.l. 
MgO-B2O3-Al2O3 ternary glass system; Crystallization; Thermal expansion