The ceramic materials used to make superconductors are a class of materials called perovskites. The superconductor we will be experimenting with is an yttrium (Y), barium (Ba) and copper (Cu) composition. Chemical formula is YBa2Cu3O7. This superconductor has a critical transition temperature around 90K, well above liquid nitrogen's 77K temperature.
Superconductors are readily available through a number of science supply stores. The YBa2Cu3O7 superconductor material, along with a rare earth magnet to demonstrate the Meissner effect is available for $40.00 (Item #K1).
Type I and Type II Superconductors
As Onnes discovered, the superconductivity of a material can be quenched when the material is exposed to a high enough (depending upon the material) magnetic field. The first superconductors discover were easily quench by relatively weak magnetic fields HC. These are type I superconductors.
Type II superconductors are more robust. They have two critical magnetic fields. The first is a low intensity magnetic field HC1 that partial quenches the superconductivity of material. The second is a high intensity magnetic field HC2 that completely extinguishes superconductivity.
The type II superconductors allow sufficient current to flow to generate strong superconducting magnets. The superconductors we are working with are type II.