Superconductivity is a phenomenon observed in several metals and ceramic materials. When these materials are cooled to temperatures ranging from near absolute zero ( 0 degrees Kelvin, -273 degrees Celsius) to liquid nitrogen temperatures ( 77 K, -196 C), their electrical resistance drops with a jump down to zero.

Superconductivity is a phenomenon observed in several metals and ceramic materials. When these materials are cooled to temperatures ranging from near absolute zero ( 0 degrees Kelvin, -273 degrees Celsius) to liquid nitrogen temperatures ( 77 K, -196 C), their electrical resistance drops with a jump down to zero.

The temperature at which electrical resistance is zero is called the critical temperature (Tc) and this temperature is a characteristic of the material as it is shown in the following table:
Material Type Tc(K)
Zinc metal 0.88
Aluminummetal 1.19
Tin metal 3.72
Mercury metal 4.15
YBa2Cu3O7ceramic 90
TlBaCaCuO ceramic 125