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Role of MgO in lowering glass transition temperature and increasing hardness of lithium silicate glass and glass-ceramics
Journal
Ceramics International
ISSN
02728842
Date Issued
2022-05-01
Author(s)
Kolay, Santa
Bhargava, Parag
Abstract
The effect of variation of MgO (1.5, 4.5 and 7.5 mol%) content on glass structure, crystallization behavior, microstructure and mechanical properties in a Li2O–K2O–Na2O–CaO–MgO–ZrO2–Al2O3–P2O5–SiO2 glass system has been reported here. Increased amount of MgO enhanced the participation of Al2O3 as a glass network former along with [SiO4] tetrahedra, reducing the amount of non-bridging oxygen (NBO) and increasing bridging oxygen (BO) amount in glass. The increased BO in glass resulted in a polymerized glass structure which suppressed the crystallization and subsequently increased the crystallization temperature, bulk density, nano hardness, elastic modulus in the glasses as well as the corresponding glass-ceramics. MgO addition caused phase separation in higher MgO (7.5 mol%) containing glass system which resulted in larger crystals. The nano hardness (∼10 GPa) and elastic modulus (∼127 GPa) values were found to be on a much higher side in 7.5 mol% MgO containing glass-ceramics as compared to lower MgO containing glass-ceramics.
Subjects