“…The role of the number of CuO 2 planes is typical mainly for Bi 2 Sr 2 Ca n −1 Cu n O 2 n +4 , in which n represents the number of CuO 2 planes, and T c ‐values are around 10, 85, and 110 K for the superconducting phases Bi 2 Sr 2 CuO 6+ x , Bi 2 Sr 2 CaCu 2 O 8+ x , and Bi 2 Sr 2 Ca 2 Cu 3 O 10+ x , respectively 2. On the other hand, a double‐layer structure, YBa 2 Cu 3 O 7 , has a T c of ∼94 K 3. In YBa 2 Cu 3 O 7 , there are Y cations between CuO 2 planes.…”