Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement o...Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.展开更多
Defect existing form and its evolution play an important role in the thermoelectric transport process. Here different forms of Pb into the Sn Se system were introduced in order to improve the thermoelectric and mechan...Defect existing form and its evolution play an important role in the thermoelectric transport process. Here different forms of Pb into the Sn Se system were introduced in order to improve the thermoelectric and mechanical properties of Sn Se. Pb/Sn Se samples were fabricated by vacuum melting, solid phase diffusion,spark plasma sintering and annealing treatment. The element valence mapping diagram and the X-ray photoelectron spectra(XPS) characteristic peaks of Pb show that a certain amount of elemental Pb exists in the initial state, and evolves into Pb^(2+)ion after annealing treatment. The micro-structure evolution leads to significant enhancement of the power factor and the ZT value. The power factor(PF) and the ZT value for Pb/Sn Se increases to 623 μW/m/K^(2) and 1.12 at 773 K after annealing treatment, respectively.Compared with Sn Se matrix, the hardness and fracture toughness of Pb/Sn Se samples increased by about40% and 10%, respectively. Reasonable control of microstructure evolution is expected to be a design idea to improve thermoelectric and mechanical properties of Sn Se.展开更多
Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles ca...Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51641206)Shandong Natural Science Foundation Project(No.ZR2015EM013)+1 种基金Special Funds for Independent Innovation and Transformation of Achievements in Shandong Province(No.2014CGZH0911)National Key R&D Program of China(No.2016YFB0100508)
文摘Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.
基金financially supported by the National Natural Science Foundation of China (No. 51772176)the Science and Technology Development Project of Shandong Province (No.2019JZZY010303)the Shandong Natural Science(No. ZR2015EM013)。
文摘Defect existing form and its evolution play an important role in the thermoelectric transport process. Here different forms of Pb into the Sn Se system were introduced in order to improve the thermoelectric and mechanical properties of Sn Se. Pb/Sn Se samples were fabricated by vacuum melting, solid phase diffusion,spark plasma sintering and annealing treatment. The element valence mapping diagram and the X-ray photoelectron spectra(XPS) characteristic peaks of Pb show that a certain amount of elemental Pb exists in the initial state, and evolves into Pb^(2+)ion after annealing treatment. The micro-structure evolution leads to significant enhancement of the power factor and the ZT value. The power factor(PF) and the ZT value for Pb/Sn Se increases to 623 μW/m/K^(2) and 1.12 at 773 K after annealing treatment, respectively.Compared with Sn Se matrix, the hardness and fracture toughness of Pb/Sn Se samples increased by about40% and 10%, respectively. Reasonable control of microstructure evolution is expected to be a design idea to improve thermoelectric and mechanical properties of Sn Se.
基金H.C.is supported by the National Natural Science Foundation of China under project number 11774236the Ministry of Science and Technology of China under project number SQ2020YFE010418+3 种基金Open Grant of State Key Laboratory of Low Dimensional Quantum Physics at Tsinghua UniversityG.L.is supported by NSF of China(Grant No.11874263)the Sino-German mobility program(M-0006)Shanghai Technology Innovation Action Plan 2020-Integrated Circuit Technology Support Program(Project No.20DZ1100605).
文摘Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.
