Improved performances of lithium disilicate glass-ceramics by seed induced crystallization

Abstract

Self-reinforced lithium disilicate (Li2Si2O5, LD) glass-ceramics were hot pressing sintered by introducing 5 wt% Li2Si2O5 crystal seeds into two different glass compositions of SiO2-Li2O-P2O5-ZrO2-Al2O3-K2O-La2O3 (7C LD) and SiO2-Li2O-K2O-La2O3 (4C LD). The results show that the seeds play an important role in the crystallization inducement, and microstructural and property improvement of the glass, especially for the glass powder without the nucleating agent of P2O5. The microstructure features a wider bimodal grain size distribution with large rod-like crystals epitaxially grown along the seeds and small crystals nucleated from the glass powder itself, contributing to the improvement of the performance especially the fracture toughness. The specimen of 4C LD glass with the addition of 5 wt% Li2Si2O5 seeds exhibited the best comprehensive properties with a good flexural strength (396±7 MPa), improved fracture toughness (3.31±0.19 MPa·m1/2), and comparable translucency as IPS e.max. This research provides a new idea and method for the improvement of the fracture toughness of lithium disilicate glass-ceramics without affecting its aesthetic appearance, and lays the foundation for its clinical applications.

Microstructure and Mechanical Properties of Li2Si2O5 Whisker-Reinforced Glass-Ceramics

“…Li 2 O interacts with P 2 O 5 in the Li-rich regions to form Li 3 PO 4 crystal nuclei, which can occur at non-uniform nucleation sites of Li 2 SiO 3 and Li 2 Si 2 O 5 crystals according to the following reaction scheme, which was conducive to reducing the nucleation energy (Wen et al, 2007;Lodesani et al, 2020 Upon increasing the amount of Li 2 Si 2 O 5 whiskers, the whisker content in the Li-rich regions also increased. The added Li 2 Si 2 O 5 whiskers could act as nuclei sites, so the simultaneous effect of surface nucleation from the glass powders and that induced by the whiskers increased the degree of crystallization (Zhao et al, 2021). Consequently, the nucleation rate rose, and the crystallinity increased.…”

Optimization of heat treatment program and effect of heat treatment on microstructure and flexural strength of micro-nano-Li2Si2O5 whisker-reinforced glass-ceramics

“…LD whiskers with nanometer and micro scale grown from single crystal can provide more crystallization sites, which is conducive to the formation of crystallization sites and further growth of crystals. The mechanical properties are greatly improved by compressive stress reinforcement, phase transformation and bridging toughening mechanisms (Zhang et al, 2019b;Zhao et al, 2021;Yan et al, 2022). On the other hand, heat treatment processes are most efficient for intensifying the performance by adjusting crystallization phases and microstructure, such as grain shape, grain size, and distribution (Sun et al, 2021).…”

Recent advances in glass‐ceramics: Performance and toughening mechanisms in restorative dentistry

“…70 Elsaka and Elnaghy 53 glass-ceramics. However, the addition of ZrO 2 leads to an increase in the sintering temperature of glass-ceramics, and it is difficult to distribute ZrO 2 uniformly and hinder densification, making the porosity as high as 1.90%, 13 all of which will affect the results of ZrO 2 phase toughening.…”