give me the reason for superconductivity at low and at high temperatures

							
Electrical resistance in metals arises because electrons                 moving through the metal are scattered due to deviations from                 translational symmetry.  These are produced either by                 impurities, giving raise to a temperature independent                 contribution to the resistance, or by the vibrations of the                 lattice in the metal.                 
The                 temperature at which electrical resistance is zero is called the                 critical temperature (Tc)                  and this temperature is a characteristic of the material
                   In a superconductor below its critical temperature, there is                 no resistance because these scattering mechanisms are unable to hinder the motion of the current carriers.  


 Hundreds of materials are known to become superconducting at low temperatures.
Superconductors are materials that can conduct electricity with no resistance, but only at low temperatures. High temperature superconductors were first discovered in 1986 in copper-oxides, which increased the operational temperature of superconductors by more than 100°C, to -130°C and opened up a wealth of applications.
The future of superconductivity research is to find materials that can become superconductors at room temperature.Once this happens, the whole world of electronics, power and transportation will be revolutionized.