Tl
2-xBa
2Ca
2Cu
3+zO
y (Tl-2223 system) superconducting oxides with various Tl contents and Cu contents were prepared. We investigated the relation between crystal structure and superconducting property dependence of Tl and Cu content. First, we obtained an almost single-phase material at a Tl content 2-x=1.7 and the Tl-2223 phase remained the main phase in the region of 2-x≥0.631 of Tl
2-xBa
2Ca
2Cu
3O
y. T
c was about 120K for the Tl-2223 in a wide range of 0.631≤2-x≤1.761. Second, we obtained a single-phase at 2-x=1.777 and Cu content 3+z=3.284 of Tl
2-xBa
2Ca
2Cu
3+zO
y. The T
c(zero) dependence of Cu/Tl ratio, showed a maximum value of 122K at Cu/Tl ratio=2.026. Based on results of crystal structure refinements by powder neutron diffraction, it was found that the change in bond length and angle dependence of average Cu valence were similar for Tl
2-xBa
2Ca
2Cu
3O
y and Tl
2-xBa
2Ca
2Cu
3+zO
y. However, the structural change dependence on average Cu valence of Tl
2-xBa
2Ca
2Cu
3O
y was large as compared to that of Tl
2-xBa
2Ca
2Cu
3+zO
y, because the substitution of Cu for Tl causes only a limited distortion of the crystal structure. Moreover, the T
c dependence on average Cu valence shows the same tendency for Tl
2-xBa
2Ca
2Cu
3O
y and Tl
2-xBa
2Ca
2Cu
3+zO
y. T
c(zero) reached the highest value of 122K at-2.07 of average Cu valence. T
c was related to the average Cu valence and flatness of the CuO
2 and BaO planes.
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