Abstract
Multi component lithium disilicate based glasses containing P2O5 have been synthesized by conventional melt quenching technique. The replacement of (Li2O + SiO2) by P2O5 and its nucleating effect has been discussed. Structural features of glasses were evaluated by differential thermal analysis (DTA), Fourier transform infrared (FTIR) and Raman spectroscopy. The glass samples have been converted into glass ceramics by following three stage heat treatment schedules. X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), high angle annular dark field imaging (HAADF), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HR-TEM) has been carried out for the glass ceramics. Vickers microhardness (Hv) and Vickers indentation fracture toughness (KIC) of all the glass ceramics have been measured. UV–Visible spectroscopy study has been carried out for glass ceramics to investigate the optical properties. The glass ceramic with 1.5 mol % P2O5 has the highest transmittance. Glass ceramics with P2O5 ≥ 1 mol % having Li2Si2O5 (LS2) as main phase exhibit high Hv about 6.71–6.82 GPa which is suitable for dental and armor applications.
Highlights
Lithium disilicate glass-ceramics have been attracting attention of mankind since decades because of their excellent mechanical and translucent properties
Surface crystallization dominates in pure Lithium disilicate glass ceramics which results in growth of larger crystals hampering the mechanical properties
Kissinger method has been used to calculate the activation energies of crystallization corresponding to the exothermic peaks as given by the relation (6) [12,14]: ln TP, α, R and ν are the peak temperature observed, heating rate used in differential thermal analysis (DTA), universal gas constant and frequency factor respectively
Summary
Lithium disilicate glass-ceramics have been attracting attention of mankind since decades because of their excellent mechanical and translucent properties. Surface crystallization dominates in pure Lithium disilicate glass ceramics which results in growth of larger crystals hampering the mechanical properties. Along with the mechanical properties, transparency is another important property to be improved for lithium disilicate glass ceramics. P2O5 is one of the promising nucleating agents for reducing the crystal size and promoting bulk crystallization in Lithium disilicate glass ceramic system. Fu wang et al [8] have studied the flexural strength, microstructure and contrast ratio of Lithium disilicate glass ceramics containing P2O5 and reported that the glass ceramic with 1 mol % P2O5 showed elongated rod like Li2Si2O5 crystals and exhibited highest flexural strength. Even though Lithium disilicate glass ceramics containing P2O5 have been extensively studied the correlation between crystallinity, micro structure, microhardness, fracture toughness and optical properties of these glass ceramics has not been reported earlier
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