Bismuth strontium calcium copper oxide

Bismuth strontium calcium copper oxide (BSCCO, pronounced bisko), is a type of cuprate superconductor having the generalized chemical formula Bi₂Sr₂Ca_n−1Cu_nO_2n+4+x, with n = 2 being the most commonly studied compound (though n = 1 and n = 3 have also received significant attention). Discovered as a general class in 1988,^[1] BSCCO was the first high-temperature superconductor which did not contain a rare-earth element.

It is a cuprate superconductor, an important category of high-temperature superconductors sharing a two-dimensional layered (perovskite) structure (see figure at right) with superconductivity taking place in a copper-oxide plane. BSCCO and YBCO are the most studied cuprate superconductors.

Specific types of BSCCO are usually referred to using the sequence of the numbers of the metallic ions. Thus Bi-2201 is the n = 1 compound (Bi₂Sr₂CuO_6+x), Bi-2212 is the n = 2 compound (Bi₂Sr₂CaCu₂O_8+x), and Bi-2223 is the n = 3 compound (Bi₂Sr₂Ca₂Cu₃O_10+x).

The BSCCO family is analogous to a thallium family of high-temperature superconductors referred to as TBCCO and having the general formula Tl₂Ba₂Ca_n−1Cu_nO_2n+4+x, and a mercury family HBCCO of formula HgBa₂Ca_n−1Cu_nO_2n+2+x. There are a number of other variants of these superconducting families. In general, their critical temperature at which they become superconducting rises for the first few members and then falls. Thus Bi-2201 has T_c ≈ 33 K, Bi-2212 has T_c ≈ 96 K, Bi-2223 has T_c ≈ 108 K, and Bi-2234 has T_c ≈ 104 K. This last member is very difficult to synthesize.