Codoping the lithium superionic conductor (LISICON) Li 3.75 Ge 0.75 P 0.25 O 4 system with various aliovalent cations M (M = Mg 2+ , B 3+ , Al 3+ , Ga 3+ , and V 5+ ) was conducted via a solid-state reaction method following the chemical formula Li 3.75±y (Ge 0.75 P 0.25 ) 1−x M x O 4 to obtain highconductivity lithium ionic conductors. The highest ionic conductivity (5.1 × 10 −5 S cm −1 ) was obtained at 25 °C for Li 3.53 (Ge 0.75 P 0.25 ) 0.7 V 0.3 O 4 , which also exhibited low activation energy of 0.43(2) eV. Rietveld refinement using neutron diffraction data revealed that the Ge 4+ , P 5+ , and V 5+ cations occupied the same crystallographic site, and their ratios were consistent with the nominal ratios of Li 3.53(6) Ge 0.5264(17) P 0.1743(12) V 0.2993(7) O 4 . Compared with the framework of γ-Li 3 PO 4 , which has only two fully occupied crystallographically different tetrahedral site lithium ions (Li: 8d, Li2: 4c), two additional partially occupied crystallographic octahedral lithium ion sites that dominantly contribute to lithium conduction were detected. The codoping strategy contributed to the compositional and structural optimization of the LISICON system, affording enhanced ion-conducting properties.
Photochromic materials are widely investigated due to their vivid color transformation for many real applications. In this work, a new kind of multiangle photochromic photonic crystal (PC) material with high robustness and long durability for smart phone decoration and anticounterfeiting features is fabricated. After thermal mixing of spiropyran powder and monodisperse core-interlayer-shell (CIS) particles, a large-area and high-quality photochromic PC film has been prepared by the selfdesigned bending-induced ordering technique (BIOT). The spiropyran powder can be well dispersed in the order-structured PC system, so the perfect synergistic combination of photochromism and angle-dependent structure colors can be achieved. The color-switching test for the as-prepared photochromic PC film proved its excellent reversibility and stability. Because of the excellent flexibility of the photo-cross-linked PC films, they can be designed and cut into various shapes with high robustness and long durability. Interestingly, a temperature-controlled photochromic effect was found in this photochromic PC system. Therefore, the as-prepared photochromic PC films can play a significant role in the fields of smart decoration and anticounterfeiting by their unique color switching effects under different stimuli. More importantly, our work verified the feasibility of this route to prepare a series of large-sized advanced smart PC devices by adding versatile functional materials.
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