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Functional properties of LaxCe1?xO2?δ nanocrystals and their bulk ceramics
摘要： Structure–property correlations were investigated for LaxCe1?xO2?δ (x = 0.05, 0.15) system (for both nanoparticles and ceramic). The nanoparticles were synthesized by the co-precipitation route and characterized for their structural, catalytic and visible light driven photocatalytic properties. Synthesised LaxCe1?xO2?δ nanopowders depicted phase purity with excellent compositional control as confirmed by various structural characterisation tools. The 15% La3+-doped ceria nanoparticles portrayed superior photocatalytic properties; complete degradation (99%) of the methylene blue dye was observed within 60 min of visible light irradiation under an alkaline medium. High density (> 96%) of the ceramics (sintered at 1580 °C for 2 h) confirmed promising sinterability of the synthesised powders. The ionic conductivities of the LaxCe1?xO2?δ ceramics increased with temperature and frequency owing to enhanced oxygen vacancies in the ceria matrix as a result of doping (of La3+-ions); a maximum conductivity of ~ 8.4 × 10?2 S cm?1 was obtained at 900 °C for the 15% La3+-doped ceria ceramics at 1 MHz frequency.
关键词： LaxCe1?xO2?δ,nanocrystals,photocatalytic properties,co-precipitation,ionic conductivity,bulk ceramics
更新于2025-09-10 09:29:36
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tilt Grain Boundary on Oxygen-ion movement In Yttria-Stabilized Zirconia: Insights from molecular dynamics
摘要： We present a new methodology for investigating the combined effect of the Σ5(310)/[001] symmetric tilt grain boundary (GB) and the local cation environment in polycrystalline yttria stabilized zirconia (YSZ) on two important quantities that determine the ionic conductivity, namely, (i) the local hopping rate of O2- ion and (ii) the probability of O2--ion -vacancy pairs within the YSZ structure. How these quantities vary with distance to the GB core are estimated for the first time using waiting time distributions associated with O2- ion hop events in molecular dynamics simulations. We conclude that indeed fewer hop events occur in the presence of a GB. However, the GB effect can be felt at a far greater distance than previously believed. Most importantly, interactions between the O2- ions, nearby cations and the GB results in a hopping behavior that is different from one observed in single-crystal YSZ. Anisotropy in O2- ion movement in the vicinity of the GB is also studied. These results and the use of our novel technique have a direct implication on the development of improved models for ionic conduction in solid state electrolytes.
关键词： Ionic conductivity,molecular dynamics,yttria stabilized zirconia,grain boundary
更新于2025-09-10 09:29:36
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Mg-doping towards enhancing the composition-phase-structural stability of Li-La-zirconate based cubic garnet upon exposure to air
摘要： Mg, as a new dopant, has been found to stabilize the desired cubic garnet structure (Ia3d) of Li-La-zirconate (LLZO) and lead to Li-ion conductivities similar to those obtained with the same level of Al-doping. More importantly, Mg-doping, as opposed to Al-doping, suppresses the deleterious reactions with the atmospheric moisture/CO2, leading to stability in the composition-phase-structure upon exposure to air. Accordingly, when exposed to air, even though Al-doped LLZO pellets get spontaneously fractured/disintegrated, accompanied by reduction in ionic conductivity by ~3 orders of magnitude, Mg-doped LLZO shows no sign of cracking and almost retains the ionic conductivity measured prior to exposure.
关键词： Ionic conductivity,Mg-doping,Composition-phase-structural stability,Lithium garnet,Solid electrolyte
更新于2025-09-04 15:30:14