Cheng Meng,Xingeng Ding,Junchuan Zhao,Chunrong Ren,Huiqin Fu,Hui Yang
Rare-earth phosphates (REPO 4 ) represent one candidate to contain minor actinides separated from used nuclear fuel. In this work, the Gd 1 − x Yb x PO 4 (0 ≤ x ≤ 1) series is synthesized via conventional solid-state reaction using Gd as the surrogate for trivalent actinides (Am, Cm), with microstructure/phase structure characterized by XRD , XPS, HRTEM and SEM as well. Solid solutions of monazite- and xenotime-type compounds are observed in the system. The structural boundary between two phases is based on the experimental temperature. The monazite → xenotime transformation is most likely to occur on a (2 0 0) monazite plane along the [0 2 0] zone. The pure xenotime-type crystalline phase with Gd 0.9 Yb 0.1 PO 4 composition is obtained at 1600 °C.
Er, Y:CaF 2 particles were synthesized using the chemical precipitation method, and as-synthesized particles were calcined at different temperatures. Fourier-transform infrared spectra confirmed the elimination of residual nitrates from Er, Y:CaF 2 phosphors calcined at 600 °C. Measurements revealed that the calcined Er, Y:CaF 2 phosphors displayed a single cubic-fluorite crystal structure with regular polygon shapes. We investigated the sensitivity effects of introducing non-active Y 3+ ions as buffers on the luminescence characteristics of Er, Y:CaF 2 phosphors under 488 nm and 980 nm excitation. Two emission bands were detected in luminescence spectra. For phosphors under 980 nm excitation, a three-photon UC mechanism is identified to be involved in the generation of green and red emissions. The findings provide insights into enhancing the 2 H 11/2 / 4 S 3/2 → 4 I 15/2 transitions in Er, Y:CaF 2 phosphors by introducing Y 3+ ions as buffers.
Meng Wang,Xiaolang Liu,Wen Zhang,Hongwei Niu,Leimin Xu,Jiantao Han,Yuhao Lu
For the first time, this work investigates the synergetic impact of yttrium (Y) and aluminium (Al) co-doping on the electrochemical properties of 4.6 V LiCoO 2 (LCO) cathode for high energy density lithium-ion batteries. The optimized LCO demonstrates an impressive initial discharge capacity of 208.6 mAh g −1 in the voltage range of 3–4.6 V, along with superior structural stability , retaining over 86 % of its initial capacity even after 125 cycles at the current of 100 mA g −1 that is far higher than the capacity retention of 40 % for the pristine LCO under the same condition. Thanks to the synergistic effect , Al in Co layers enhances the bonds of Al/Co-O to stabilize oxygen in the LCO crystal structure while Y serves “pillar” in Li layers, migrated from the initial Co layers during cycling process, effectively curtail the formation and expansion of interlayer cracking, which contributes to the long-term cycle stability of LCO under high voltage. Most importantly, Al/Y co-doping is a facile process compatible with the existing industrial infrastructure for LCO mass production, and thus it can be scaled up readily for commercial applications. Al/Y co-doped LCO is assembled into commercial-level pouch cells with graphite anode, achieves an extremely high energy density of 750 Wh/L, and exhibits a superior cycling stability and obtains a capacity retention of 88.2 % at 25 °C after 800 cycles with the high cutoff voltage of 4.55 V.
The optical properties of colored cool pigments including their color and solar reflectance are predominantly governed by chemical defects.In this study, a series of yellow cool pigments SrCe 1-x Tb x O 3 (x = 0–0.3) and SrCe 0.7-x Tb 0.3 Y x O 3 (x = 0–0.1) were synthesized via the solid-state reaction based on defect engineering. The effects of chemical defects on their optical performance were systematically investigated. Tb doping extends the absorption edge of the pigments to the visible region beyond 500 nm, thereby imparting a distinct yellow hue to the pigment. However this doping process simultaneously introduces oxygen vacancy defects and facilitates the coexistence of mixed-valence cations (Ce 4+ /Ce 3+ and Tb 4+ /Tb 3+ ) within the host lattice. This results in pronounced tail absorption that compromises both color properties and solar reflectance. To address this issue, yttrium was introduced as a co-dopant following the charge compensation principle which effectively suppressed defect formation and reduced tail absorption intensity. This co-doping strategy successfully achieved a synergistic optimization of pigment color and solar reflectance. The optimized pigments exhibited a high b* value of 75 and an exceptional near-infrared reflectance of95.33 %. The simulation experiment revealed that coating based on the as-prepared pigment exhibited an internal surface temperature reduction of 15.5 °C compared to the conventional cement coating. These findings underscore that optimizing color and solar reflectance through chemical defect regulation represents a feasible approach for preparing high-performance colored cool pigments.
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