4 Two types of superconductor
The two main types of superconducting materials are known as type-I and type-II superconductors, and their properties will be discussed in the remainder of this course. All of the pure elemental superconductors are type-I, with the exception of niobium, vanadium and technetium. The discussion of the effects of magnetic fields and currents on superconductors earlier in this course has been confined to thin cylinders of type-I materials like lead or tin in a parallel magnetic field. In Subsection 4.1 we shall discuss what happens when the magnetic field is perpendicular to cylinders made of these materials.
Superconducting alloys and high critical temperature ceramics are all type-II, and these are the materials that are used in most practical applications. In Subsection 4.2, we shall consider the response to a magnetic field of this type of superconductor. Such materials behave quite differently from lead and tin, and this is the reason that they are widely used.