To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiate...To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.展开更多
The early precipitation ofγ’-Co3(Al,W)phase affects the spatial distribution and kinetic evolution of precipitates for the morphology transmission effect,but the nucleation and concomitant growth are not studied sti...The early precipitation ofγ’-Co3(Al,W)phase affects the spatial distribution and kinetic evolution of precipitates for the morphology transmission effect,but the nucleation and concomitant growth are not studied still by aging experiments due to the expeditious precipitation ofγ’phase in Co-Al-W alloy.By using the phase-field simulation with sublattice free energy,the early-stage kinetics evolution ofγ’-Co3(Al,W)phase in a medium supersaturation Co-9 Al-8 W(at.%)alloy aged from 1023 K to 1173 K is investigated.The influences of aging temperature on the evolution of morphology and composition ofγ’phase,and the kinetics of nucleation and growth to coarsening are clarified.It is found that the rates of composition evolution of W inγphase are two or three times that ofγ’phase,and the W compositions inγandγ’phases show a linear relationship with time t–1/3,which means that the coarsening takes place earlier at high temperature.In addition,the equilibrium partitioning ratios indicate Al and W partition into theγ’phase and the ratios decrease with elevated temperature.The compositional variations across theγ/γ’phase interfaces suggest that low aging temperature makes the stoichiometric ratio closer to 3:1.Moreover,the precipitation evolutions from early nucleation to growth and coarsening in Co-Al-W alloy are distinguished,and the rate constants of square and cube of average particles radius increase with temperature.In later growth stage,the relationship of the square of average particles radius and time is obeyed,while the steady-state coarsening stage follows the cube law.The time exponents of particles number density at the coarsening stage are close to–1 of Kuehmann-Voorhees(KV)theory.The study demonstrates that the early-stage evolution ofγ’phase which is undiscovered in the experiment can be captured by the phase-field simulation,and the resultant kinetics laws agree well with the experimental and theoretical results.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61473023)the Aerospace Science and Technology Innovation Fund,CASCInternational S&T Cooperation Program of China(ISTCP)(Grant No.2015DFR80190)
文摘To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.
基金financially supported by the National Natural Science Foundation of China(No.51571122)the Fundamental Research Funds for the Central Universities(No.30916015107)。
文摘The early precipitation ofγ’-Co3(Al,W)phase affects the spatial distribution and kinetic evolution of precipitates for the morphology transmission effect,but the nucleation and concomitant growth are not studied still by aging experiments due to the expeditious precipitation ofγ’phase in Co-Al-W alloy.By using the phase-field simulation with sublattice free energy,the early-stage kinetics evolution ofγ’-Co3(Al,W)phase in a medium supersaturation Co-9 Al-8 W(at.%)alloy aged from 1023 K to 1173 K is investigated.The influences of aging temperature on the evolution of morphology and composition ofγ’phase,and the kinetics of nucleation and growth to coarsening are clarified.It is found that the rates of composition evolution of W inγphase are two or three times that ofγ’phase,and the W compositions inγandγ’phases show a linear relationship with time t–1/3,which means that the coarsening takes place earlier at high temperature.In addition,the equilibrium partitioning ratios indicate Al and W partition into theγ’phase and the ratios decrease with elevated temperature.The compositional variations across theγ/γ’phase interfaces suggest that low aging temperature makes the stoichiometric ratio closer to 3:1.Moreover,the precipitation evolutions from early nucleation to growth and coarsening in Co-Al-W alloy are distinguished,and the rate constants of square and cube of average particles radius increase with temperature.In later growth stage,the relationship of the square of average particles radius and time is obeyed,while the steady-state coarsening stage follows the cube law.The time exponents of particles number density at the coarsening stage are close to–1 of Kuehmann-Voorhees(KV)theory.The study demonstrates that the early-stage evolution ofγ’phase which is undiscovered in the experiment can be captured by the phase-field simulation,and the resultant kinetics laws agree well with the experimental and theoretical results.
