Crystallization of pyroxene phases and physico-chemical properties of glass-ceramics based on Li2O–Cr2O3–SiO2 eutectic glass system

Abstract

The crystallization characteristics, crystalline phase assemblages and solid solution phases developed due to thermally crystallized glasses based on the Li2SiO3–Li2Si2O5–LiCrSi2O6 (1028 ± 3 °C) eutectic glass system by replacing some trivalent oxides instead of Cr2O3 were investigated. The microhardness and chemical durability of the glass-ceramics were also determined. Lithium meta and disilicate (Li2SiO3 and Li2Si2O5), lithium gallium silicate (LiGaSiO4), and varieties of pyroxene phases, including Cr-pyroxene phase, i.e. lithium-kosmochlor (LiCrSi2O6), lithium aluminum silicate (LiAlSi2O6), lithium indium silicate (LiInSi2O6) and pyroxene solid solution of Li-aegerine type [Li (Fe0.5, Cr0.5) Si2O6] were the main crystalline phases formed in the crystallized glasses. There is no evidence for the formation of solid solution or liquid immiscibility gaps between LiAlSi2O6 or LiInSi2O6 phases and LiCrSi2O6 phase. However, LiCrSi2O6 and LiFeSi2O6 components were accommodated in the pyroxene structure under favorable conditions of crystallization to form monomineralic pyroxene solid solution phase of the probably formula [Li (Fe0.5, Cr0.5) Si2O6]. The type and compatibility of the crystallized phases are discussed in relation to the compositional variation of the glasses and heat-treatment applied. The microhardness values of the crystalline materials ranged between 5282 and 6419 MPa while, the results showed that the chemical stability of the glass-ceramics was better in alkaline than in acidic media.