23 September 2012

High Temperature Superconductivity

In 1986, a major break through in superconductivity took place. They observed highest Tc had done from 4K to about 23K. Chu and co-workers formed Y-Ba-Cu-O system with transition temperature of 90K. 

Any superconductor with a transition temperature above 10K is in general called high temperature superconductor.

In the table year of discovery and critical temperature Tc of high temperature superconductors are given.

Year          Material                            Tc / K

1974         LiTi2O4                                      13

1975         Ba(PbBi)O3                          13

1986         La2-xSrxCuO4                       38

1987         YBa2Cu3O7                           92

1988          Tl2Ca2Ba2Cu3O10                125

General Characteristics:

1. They have high transition temperature.

2. They are direction dependent.

3. They have pervoskite crystal structure.

4. They are reactive, brittle and cannot be easily formed or joined.

5. They are oxides of copper in combination with other elements.

6. They are also called as 1-2-3 compound.