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Phase and microstructural evolution in lithium silicate glass‐ceramics with externally added nucleating agent
Author(s) -
Kolay Santa,
Bhargava Parag
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16682
Subject(s) - lithium (medication) , materials science , crystallization , silicate , sintering , glass ceramic , nucleation , phase (matter) , mineralogy , ceramic , silicate glass , lithium disilicate , chemical engineering , composite material , chemistry , medicine , organic chemistry , engineering , endocrinology
Development of lithium disilicate‐based glass‐ceramics critically depends on use of nucleating agent in the glass matrix. The present study reports the effect of externally added nucleating agent Li 3 PO 4 in Li 2 O–K 2 O–MgO–ZnO–ZrO 2 –Al 2 O 3 –SiO 2 system which is compared with a reference composition (GC1) (SiO 2 :Li 2 O = 2.16:1) prepared with in situ formed Li 3 PO 4 . For externally added Li 3 PO 4 , two compositions were studied. In one case (GC2) before addition of Li 3 PO 4 , SiO 2 :Li 2 O ratio in glass was maintained as 2.87:1 and in another case (GC3) SiO 2 :Li 2 O ratio in glass was maintained same as reference GC1 that is, 2.16:1. The glasses were characterized by using MAS‐NMR spectroscopy. Sintering and crystallization behavior of the glass‐ceramics was characterized by using XRD, SEM, DTA. Due to in situ formation of Li 3 PO 4 , GC1 resulted in a dense sample with finer crystals of lithium disilicate. In GC2 and GC3, externally added lithium phosphate, which was in the form of ultrafine aggregated particles, formed flower‐like colonies of radially outward crystals. Higher SiO 2 :Li 2 O ratio in GC2 resulted in lithium disilicate crystals and high viscous glass causing large air entrapment and so less densification. GC3 with higher lithia in glass showed higher densification than GC2 but only lithium metasilicate crystals were formed.