|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1998 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
The fluorination of La_<2-x>Sr_xCuO_<4-y> was carried out for fluorine introduction to layered copper oxide. In addition to the fluorination by the reaction with La_<2-x>Sr_xCuO_<4-y> and CuF_2, reported previously, the reaction with NH_4F was also tried. It became clear in La_<2-> La_<2-x>Sr_xCu(O,F)_<4-z> which was synthesized by the reaction with CuF_2 the superconductivity appeared by the fluorine treatment in a Sr rich region. There is a report with electronic carrier type oxide superconductivity as for this compound, but the obtained sample was confirmed to be a hole carrier type instead of the electron carrier type by examining the average atomic value of copper of the sample by iodine titration method. The superconductivity didn't appear with La_<0.7>Sr_<1.3>Cu(O,F)_<4-z>, which was reported to be a superconductor, and the superconductivity appeared only in Sr_2CuO_2F_<2+z> which is the fluorination compound of Sr_2CuO_3, in this solid solution compounds. In the previous report
, synthesis temperature is lower than the current report, and Sr_2CuO_3 may coexist as a impurity in sample of this composition La_<0.7>Sr_<1.3>Cu(O,F)_<4-z>. It is thought that the superconductivity of a very small amount of Sr_2CuO_2F_<2+z> misunderstand to be the bulk property. Because a and axes of the crystals increased by the fluorination, fluorine was introduced indeed into the crystals even in La_<0.7>Sr_<1.3>Cu(O,F)_<4-z> which didn't appear the superconductivity. It is thought however that CuO_2 plane which superconductivity was carried on didn't restructured. The superconductivity of Sr_2CuO_2F_<2+z> was characterized by the heat capacity measurement, and it became clear the similar superconductivity characteristic to the hole carrier type superconductors with T structure. On the other hand, no superconductivity appeared by fluorination treatment with NH_4F and it showed a semiconductive behavior. This results show that we can control the properties of the fluorination compounds by synthesis process.