Oxide high-temperature superconductor and its production method

An oxide high temperature superconductor comprising a crystalline substrate, a first buffer layer formed on said crystalline substrate, a second buffer layer formed on said first buffer layer, and an oxide high temperature superconductor thin film formed on said second buffer layer, wherein

• said first buffer layer is made of CeO2,
• said second buffer layer has a composition formula:
• Cu1−xMxSr2CaCu2O8−w,
• said oxide high temperature superconductor thin film has a composition formula:
• (Cu1−xMx)2(Ba1−ySry)2(Ca1−zLz)n−1(Cu1−qQq)nO2n+4−w,
• M represents Tl, Hg, Bi, Pb, In, Ga, Al, B, C, Si, Sn, Ag, Au, S, N, P, Mo, Re, Os, Cr, Ti, V, Fe, one element in the lanthanide series, or one or more alkali metal elements,
• L represents Mg, Y, or one or more elements in the lanthanide series,
• Q represents either or both of Mg and Zn,
• 0≦x≦1, 0≦y<1, 0≦z≦1, 0≦q<0.1, 0≦w≦4, and 2≦n≦5;
• wherein said second buffer layer completely overlies the first buffer layer, and said oxide superconductor thin film has a uniform orientation, and said crystalline substrate is a sapphire substrate.