The objective of this study was to evaluate the effects of P 2 O 5 particle size distribution on the crystalline phases and microstructure of lithium disilicate glass-ceramics derived from the TiO 2 -ZrO 2 -Li 2 O-CaO-Al 2 O 3 -SiO 2 system for dentistry applications. The samples were made via fusion and casting procedure. Crystallisation as well as the morphology and microstructure of the samples were investigated using X-ray diffraction, differential scanning calorimetric and scanning electron microscopy. The results showed that the crystallisation of the samples occurred in the range of 500-650uC. The main crystalline phase was lithium disilicate (Li 2 Si 2 O 5 ) along with Lithium metasilicate (Li 2 SiO 3 ), spodumene [LiAl(SiO 3 ) 2 ], lithium orthophosphate (Li 3 PO 4 ) and cristobalite as secondary phases. With decreasing size of P 2 O 5 particles, the morphology of Li 2 Si 2 O 5 crystals was transformed from needle shaped to spherical-like and the mechanical property was improved. The optimal flexural strength of 280 MPa and microhardness of 620 HV were obtained at the lithium disilicate glass-ceramics with P 2 O 5 nanoparticles.
In this research, NASICON type (LiZrXTi2-X(PO4)3) glass-ceramics were fabricated (x = 0.1, 0.2, 0.3, 0.4). Lithium-ion conductivity along with the crystallization tendency and microstructural features were examined in this regard. Parent glasses obtained through melt quenching were converted to the glass-ceramic specimens after one-step heat treatment procedure. The resultant glass-ceramics were deeply explored by means of different techniques including scanning electron microscope, differential thermal analysis, X-ray diffractometry, and ionic conductivity measurements. According to the obtained results, presence of Zr4+ ions in the glass network and its gradual increase caused the enhanced crystallization temperature as well as declined crystallinity and microstructure coarsening. In all studied glass-ceramics, LiT2(PO4)3 solid solution was the dominant crystalline phase and Zr4+ ions partly substituted in the structure of this crystalline phase. Moreover, presence of Zr4+ ions in the glass composition resulted in diminished lithium-ion conductivity of corresponded glass-ceramics at ambient temperature. Consequently, total conductivity of specimen with the highest level of ZrO2 (x = 0.4) was measured to be 0.78 x 10-5 Scm-1, being considerably less than ionic conductivity of the base (x = 0) glass-ceramic (3.04 x 10-5 Scm-1). It seems that less crystallinity of ZrO2 containing glass-ceramics decreases required connectivity between the lithium-ion free paths and is responsible for the diminished ionic conductivity of these specimens.
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