Tu Qingyun

Zero resistance at 148.5K in fluorine implanted YBaCuO compound

Abstract Fluorine ions with an energy of 180keV at a dose of 1×10 15 ions/cm 2 have been implanted into YBa 2 Cu 3 O x . After annealed at 800°C, the resistance of the new Y-Ba-Cu-F-O compound drops to zero at 148.5K.

Infrared spectra of the high-Tc TlBaCaCuO superconductors

Abstract The TlBaCaCuO superconductors with zero resistance at temperatures in the range of 100–123 K have been sintered by solid state reactions. Electron microscopy and X-ray diffraction studies reveal that they are multiphased, containing both Tl 2 Ba 2 CaCu 2 O 8 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 superconducting phases. Infrared spectra have been measured at room temperature for the multiphase samples. The spectra display structures at ∼590 cm -1 ( P 1 ) and ∼530 cm -1 ( P 2 ) which seem characteristic to Cu-O stretching modes. The difference Δ P between P 1 and P 1 has been found to be related to the superconducting transition temperature. Smaller Δ P corresponds to a higher T c . The electron-like excitation of∼0.1 eV and the phonon-like structure at ∼850 cm -1 are also found to be important for high T c .

Sn Substitution of TlBaCaCuO Superconductors

In order to study how the Sn substitution for Tl changes the superconducting properties of the TlBaCaCuO compound, we have prepared samples with Sn in place of Tl by solid state reactions. Measurements of resistance and magnetic susceptibility show that partial substitution of Tl with Sn is helpful to form the superconducting 2223 phase (for Tl:Ba:Ca:Cu). It has been found that samples mainly contain tetragonal phase 2223, but there also exist a few additional mixed phases like 1223, 1234 and nonsuperconducting phase BaSnO3.

Possible high Al substitution in the Tl-Ba-Ca-Cu-O superconducting system

The Al substitution in the Tl-Ba-Ca-Cu-O superconducting system was studied. Up to 70% of Tl can be substituted by Al, without significant reduction of Tc. X-ray diffraction indicates partial Al substitution does not alter the crystal structure of the 2223 phase. Excessive Al formed Al-Cu alloy and unidentified phases, which gradually destroyed the superconductivity.

Superconductivity in Mo films after implanting Be ions

Abstract We have studied superconductivity and the temperature dependence of resistance in amorphous Mo 0.65 Be 0.35 thin films (∼1100 A) prepared by implanting Be ions into Mo films. The high Debye temperature of Be increases the T c of annealed recrystallized MoBe thin films, but not that of the amorphous films.