CONTRIBUTION OF SOME METAL OXIDES TO CRYSTALLIZATION CHARACTERISTICS OF LITHIUM BOROSILICATE GLADDES

Abstract

A systematic study on the crystallization characteristics of some glasses based on the Li2 0-B2 0rSi02 system was carried out. The base glass composition was modified by introducing ZnO, MnO (or with MgO or CaO), or Fe2 03 instead of B2 03• Ab03 was also added to some selected modified glasses. However, in' the base glass composition AI 203 was also introduced as an addition or instead of Li2 0. Titanium dioxide was used as a crystallization catalyst.

The thermal behaviour of the investigated glasses was studied by differential thermal analysis technique. The glasses, therefore, were heated through different heat-treatment sche­ dules based on the DTA data. The crystalline phase assem­ blages and the resultant microcrystalline structures of the heat­ treated glasses were investigated in relation to their basic chemical compositions and heat-treatment parameters by using the X-ray diffractometry and scanning electron microscopy. The chemical durability, using acid solution, for the glasses and glass-ceramics were determined.

Different crystalline phase assemblages, including lith­ ium meta-and di-silicate, lithium meta-, di-,tri-,tetra-and pyro­ borate, lithium zinc orthosilicate, braunite, a-quartz, tephorite, kanoite, bustamite, Mn-wollastonite ss, lithium iron silicate, lithium ferrite, lithium ferrate, iron oxide, P-eucryptite ss, and P-spodumene ss, were crystallized from the investigated glasses using various heat-treatment process. The type, stabi­ lity and compatibility of the crystalline phases formed, were discussed in relation to glass composition and thermal treatment.