Zhou Mei-ling

Effect of F Doping on Fabrication and Superconductivity of SmO1-xFδFeAs Compound

Abstract We report the effect of fluorine doping on the fabrication and superconductivity of the iron-based arsenic oxide SmO1-xFδFeAs (δ≥x) compound. The fluorine over-doping can greatly reduce the heat treatment temperature and the heat treatment time, meanwhile the superconductivity of the SmO1-xFδFeAs samples does not reduce. The critical transition temperature (Tc) is as high as 56.5 K for the SmO0.7F0.3FeAs sample prepared by the two-step solid state reaction method at 1120 °C for 40 h, the Jc of the sample is 2.4×105 A/cm2 (10 K, 0 T). Tc of the fluorine over-doped SmO0.7F0.35FeAs and SmO0.7F0.4FeAs samples prepared by the two-step solid state reaction method at 1100 °C for 20 h are 56 and 55 K, respectively. Jc of the both samples are 1.9×105 and 1.7×105 A/cm2 (10 K, 0 T), respectively.

Study on emission stability of Mo-La/sub 2/O/sub 3/ cathode

The Mo-La/sub 2/O/sub 3/ cathode, which possesses the advantages of high strength and good ambient ductility, excellent electron emission ability, low operating temperature and radioactive-free pollution, is a promising cathode for replacing W-ThO/sub 2/ cathode in a variety of vacuum electron devices. However, it was found that the emission current of Mo-La/sub 2/O/sub 3/ cathode electron tubes attenuated with lifetime rapidly. In order to obtain stable emission of Mo-La/sub 2/O/sub 3/ tubes, much effort have been done on the material composition, the carbonizing process and emission mechanism in recent years. The results obtained indicate that the great progress has been made in the emission stability and the lifetime of Mo-La/sub 2/O/sub 3/ cathode tubes. The Mo-La/sub 2/O/sub 3/ cathodes have been successfully used to replace W-ThO/sub 2/ cathodes in FU-6051 electron tubes in China gradually.