60 research outputs found
Microscopic annealing process and its impact on superconductivity in T'-structure electron-doped copper oxides
High-transition-temperature superconductivity arises in copper oxides when
holes or electrons are doped into the CuO2 planes of their insulating parent
compounds. While hole-doping quickly induces metallic behavior and
superconductivity in many cuprates, electron-doping alone is insufficient in
materials such as R2CuO4 (R is Nd, Pr, La, Ce, etc.), where it is necessary to
anneal an as-grown sample in a low-oxygen environment to remove a tiny amount
of oxygen in order to induce superconductivity. Here we show that the
microscopic process of oxygen reduction repairs Cu deficiencies in the as-grown
materials and creates oxygen vacancies in the stoichiometric CuO2 planes,
effectively reducing disorder and providing itinerant carriers for
superconductivity. The resolution of this long-standing materials issue
suggests that the fundamental mechanism for superconductivity is the same for
electron- and hole-doped copper oxides.Comment: 23 pages, 3 figures, accepted for publication in Nature Material
An oxalate cathode for lithium ion batteries with combined cationic and polyanionic redox
Authors acknowledge financial support from the National Natural Science Foundation of China (51822210), the Australian Research Council (ARC) for its support through Discover Project (DP 140100193),Shenzhen Peacock Plan (KQJSCX20170331161244761), the Program for Guangdong Innovative and Entrepreneurial Teams (No. 2017ZT07C341), and the Development and Reform Commission of Shenzhen Municipality for the development of the “Low-Dimensional Materials and Devices” discipline.The growing demand for advanced lithium-ion batteries calls for the continued development of high-performance positive electrode materials. Polyoxyanion compounds are receiving considerable interest as alternative cathodes to conventional oxides due to their advantages in cost, safety and environmental friendliness. However, polyanionic cathodes reported so far rely heavily upon transition-metal redox reactions for lithium transfer. Here we show a polyanionic insertion material, Li2Fe(C2O4)2, in which in addition to iron redox activity, the oxalate group itself also shows redox behavior enabling reversible charge/discharge and high capacity without gas evolution. The current study gives oxalate a role as a family of cathode materials and suggests a direction for the identification and design of electrode materials with polyanionic frameworks.Publisher PDFPeer reviewe
Niedermayrit, Cu4Cd(SO4)2(OH)6 � 4H2O, ein neues Mineral aus dem Bergbaugebiet Lavrion, Griechenland
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