Comparison of Type – I and Type – II Superconductors

Type I and Type II superconductors are two magnetic classes of materials that conduct electricity with vanishing DC resistance below a critical temperature, based on the properties of Superconductors. The split is not the same as low-temperature versus high-temperature superconductors.
(1) Type – I Superconductors: a single critical field and a full Meissner state. Most elemental examples are also low-temperature superconductors.
(2) Type – II Superconductors: two critical fields and a mixed state between them. This class includes low-temperature alloys such as NbTi and high-temperature cuprate oxides.
The comparison of type-I and type – II superconductors is shown in the table below

Type – I Superconductors	Type – II Superconductors
Critical temperature often below about 10 K for elemental Type I	Critical temperature can be low (NbTi near 9 K) or much higher in cuprate oxides
Low critical magnetic field (often well below 1 T for elemental Type I)	Upper critical field can exceed 1 T and reach tens of tesla in technical Type II wires
Shows a full Meissner effect below the single critical field: the magnetic field is expelled from the bulk.	Shows a full Meissner effect only below the lower critical field. Between the two critical fields, flux vortices enter the mixed state.
Exhibits single critical magnetic field.	Exhibits two critical magnetic field
Easily lose the superconducting state by low-intensity magnetic field. Therefore, type-I superconductors are also known as soft superconductors.	Does not easily lose the superconducting state by external magnetic field. Therefore, type-II superconductors are also known as hard superconductors.
Type-I superconductors transition sharply and abruptly from a superconducting state to a normal state under external magnetic fields.	Type-II superconductors gradually transition from a superconducting state to a normal state under external magnetic fields, but the change is not sharp. At lower critical magnetic field (HC1), type-II superconductor starts losing its superconductivity. At upper critical magnetic field (HC2), type-II superconductor completely loses its superconductivity. The state between lower critical magnetic field and upper magnetic field is known as an intermediate state or mixed state.
Due to the low critical magnetic field, type-I superconductors cannot be used for manufacturing electromagnets used for producing strong magnetic field.	Due to the high critical magnetic field, type-II superconductors can be used for manufacturing electromagnets used for producing strong magnetic field.
Generally, Type-I superconductors are composed of pure metals.	Type-II superconductors are generally alloys and complex oxides of ceramics.
BCS theory explains conventional Type I superconductivity.	BCS theory also explains conventional Type II alloys such as NbTi. It does not fully explain cuprate high-temperature Type II oxides.
These are completely diamagnetic.	These are not completely diamagnetic
These are also called as Soft Superconductors.	These are also called as Hard Superconductors.
These are often called low-temperature superconductors when they are elemental metals, but that label is not the Type I definition.	These include both low-temperature alloys and high-temperature oxides. High-Tc is not the Type II definition.
No mixed state exists in type-I Superconductors.	A mixed state exists in type-II Superconductors.
Small amounts of impurity usually leave the Type I transition intact if the field stays below the critical value.	Defects in Type II can pin flux and actually help magnet wire carry current; they do not simply destroy superconductivity.
Due to the low critical magnetic field, type-I superconductors have limited technical applications.	Due to the high critical magnetic field, type-II superconductors have wider technical applications.
Examples: Hg, Pb, Zn,etc.	Examples: NbTi, Nb3Sn, etc.