Conventional superconductors are materials that display superconductivity as described by BCS theory or its extensions.
Critical temperatures of some simple metals:
Niobium and vanadium are type-II superconductors, while most other superconducting elements are type-I materials. Almost all compound and alloy superconductors are type-II materials.
The most commonly used conventional superconductor in applications is a niobium-titanium alloy - this is a type-II superconductor with a Tc of 11 K. The highest critical temperature so far achieved in a conventional superconductor was 39 K (-234 °C) in magnesium diboride.