The polyacrylamide gel method has been developed for fabrication of Ba1-xSrxTiO3 (BST, x=0.1-0.5) photocatalysts. When x=0.1-02, BST photocatalyst is tetragonal phase, and when x is other values, BST photocatalyst is...
Herein,
based on powder and single-crystal diffractions of the
samples synthesized, and density functional theory (DFT) calculations,
we investigated the crystal structure of the Li2+x
C1–x
B
x
O3 (LCBO) solid solution ss1 (Li2CO3 phase, 0 ≤ x < 0.35) electrolyte.
Besides the Li1 site, three interstitial lithium sites [Li2 (8f),
Li3 (8f), and Li4 (8f)] are observed. Most of the Li+ are
located at site Li1 with the occupancy (occLi1) > 0.80(1)
and the occLi1 decreases as x increases
[occLi1 = 0.92(1), 0.82(1), and 0.82(1) in Li2.1C0.9B0.1O3, Li2.2C0.8B0.2O3, and Li2.3C0.7B0.3O3, respectively]. The interstitial
Li+ occupy the site Li2 with occLi2 + occLi1 ≈ 1.0 and Li3, Li4 sites. We carried out theoretical
calculations/optimizations to check the energy-preferred structural
geometry; Li1 is the most energy-preferred site in both Li2CO3 and Li9C3BO12. We
also investigated the ionic conductivity and Li+ migrations
of Li2+x
C1–x
B
x
O3 ss1. The continuous
−Li3–s1–Li2–s2–Li1–s3–Li3–
one-dimensional (1D) pathway (through s1–s3 saddle sites) shows
the lowest barrier energy (0.094–0.29 eV). The 1D paths are
then connected by the saddle sites s4 (0.31 eV) and s5 (0.48 eV) with
a higher barrier energy to form a curved two-dimensional (2D) migration
pathway in the a–c plane,
and are connected by Li4 through the saddle site s8 (0.49–0.55
eV) to form a three-dimensional (3D) framework migration pathway.
The Li+ migration is dominated by the −Li3–s1–Li2–s2–Li1–s3–Li3–
1D pathway at T ≤ 75 °C and by 1D, 2D,
and 3D pathways at T ≥ 100 °C.
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