Effect of Ag_2O Addition in Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8 on the Structure and Contact Resistivity of Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8/Ag

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Effects of Ag_2O addition in Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8 on the structure and the contact resistivity of Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8/Ag interfaces have been investigated by the measurements of X-ray diffraction and contact resistivity. For Ag_2O-free specimens, they must be sintered three times at 800℃ for 24 h with intermediate grinding to obtain the pure 124 phase. However, with addition of 25 wt% Ag_2O in Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8, the single 1-2-4 phase can be formed with sinted only one time at 800℃ for 24 h. The lowest ohmic-contact resistivity annealing 4.55×10^<-5> Ω・cm^2 at 300 K and less than 10^<-8> below T_c for Ag_2O-free system are observed by annealing at 600℃ for 1 h under one oxygen atmosphere. With addition of 25 wt% Ag_2O in Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8, the optimal annealing temperature to obtain the lowest ohmic-contact resistivity can be improved down to 400℃. In fact, a low-resistivity ohmic contact for the Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8/Ag interface can be achieved without any thermal annealing just by the addition of 25 wt% Ag_2O in Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8. These results indicate that the addition of Ag_2O can aid the formation of the 1-2-4 phase and upgrade effectively the characteristics of Y_<0.9>Ca_<0.1>Ba_2Cu_4O_8/Ag interfaces to get better ohmic contact even without annealing, resulting in a lower annealing temperature and contact resistivity.
社団法人応用物理学会の論文
1996-01-15