The garnet-type Li7La3Zr2O12 (LLZO) belonging to cubic symmetry (space group Ia3̅d) is considered as one of the
most promising solid electrolyte materials for all-solid state lithium
ion batteries. In this study, the diffusion coefficient and site occupancy
of Li ions within the 3D network structure of the cubic LLZO framework
have been investigated using ab initio molecular dynamics calculations.
The bulk conductivity at 300 K is estimated to be about 1.06 ×
10–4 S cm–1 with an energy barrier
of 0.331 eV, in reasonable agreement with experimental results. The
complex mechanism for self-diffusion of Li ions can be viewed as a
concerted migration governed by two crucial features: (i) the restriction
imposed for occupied site-to-site interatomic separation, and (ii)
the unstable residence of Li ion at the 24d site, which can serve
as the trigger for ion mobility and reconfiguration of surrounding
Li neighbors to accommodate the initiated movement. Evidence for Li
ordering is also found at low temperature for the LLZO system.
Garnet-type Li7La3Zr2O12 (LLZrO) is a candidate solid electrolyte material that is now being intensively optimized for application in commercially competitive solid state Li+ ion batteries. In this study we investigate, by force-field-based simulations, the effects of Ga3+ doping in LLZrO. We confirm the stabilizing effect of Ga3+ on the cubic phase. We also determine that Ga3+ addition does not lead to any appreciable structural distortion. Li site connectivity is not significantly deteriorated by the Ga3+ addition (>90% connectivity retained up to x = 0.30 in Li7–3xGaxLa3Zr2O12). Interestingly, two compositional regions are predicted for bulk Li+ ion conductivity in the cubic phase: (i) a decreasing trend for 0 ≤ x ≤ 0.10 and (ii) a relatively flat trend for 0.10 < x ≤ 0.30. This conductivity behavior is explained by combining analyses using percolation theory, van Hove space time correlation, the radial distribution function, and trajectory density
The low rigidity type titanium alloy, Ti-29Nb-13Ta-4.6Zr was designed, and then the practical level ingot of the alloy was successfully fabricated by Levicast method. The mechanical and biological compatibilities of the alloys were investigated in this study. The following results were obtained. The mechanical performance of tensile properties and fatigue strength of the alloy are equal to or greater than those of conventional biomedical Ti-6Al-4V ELI. Young's modulus of the alloy is much lower than that of Ti-6Al-4V ELI, and increases with the precipitation of α phase or ω phase in the β matrix phase. The compatibility of the alloy with bone of the alloy is excellent. Low rigidity of the alloy is effective to enhance the healing of bone fracture and remodeling of bone. The bioactive coating layer of hydroxyapatite can be formed on the alloy.
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