superconducting transition

A transition at the critical temperature, $T c$ , below which the resistance of electrical conductors becomes zero and magnetic flux is excluded. Examples: The transitions of Nb₃Sn, Nb₃Al and V₃Si to superconductors ( $15 K < T c < 20 K$ ) and YBa₂Cu₃O_7-x ( $x ≈ 0.2$ ) at $90 K$ .

Source:

PAC, 1994, 66, 577 (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 592