Materials

1. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science

2. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
WHAT IS SUPERCONDUCTIVITY??
For some materials, the resistivity vanishes at some low temperature:
they become superconducting.
Superconductivity is the ability of
certain materials to conduct
electrical current with no resistance.
Thus, superconductors can carry
large amounts of current with little
or no loss of energy.
Type I superconductors: pure metals, have low critical field
Type II superconductors: primarily of alloys or intermetallic compounds

3. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
MEISSNER EFFECT
B
T >Tc T < Tc
B
When you place a superconductor in a magnetic field, the field is expelled below TC.
Magnet
Superconductor
Currents i appear, to cancel B.
i x B on the superconductor
produces repulsion.

4. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
A superconductor displaying the MEISSNER EFFECT
Superconductors have electronic and magnetic properties. That is, they have a
negative susceptibility, and acquire a polarization OPPOSITE to an applied magnetic
field. This is the reason that superconducting materials and magnets repel one
another.
If the temperature increases the sample will lose its superconductivity and the
magnet cannot float on the superconductor.

5. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
Record TC versus Year Discovered
0
20
40
60
80
100
120
140
160
180
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Year
T
C
(K)
Hg
NbN
Nb3Ge
La-Ba-Cu-O
La-Sr-Cu-O
YBa2Cu3O7
Bi2Sr2Ca2Cu3O8
Tl-Ba-Ca-Cu-O
HgBa2Ca2Cu2O8
HgBa2Ca2Cu2O8 Pressure
1986

6. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science

7. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
APPLICATIONS:
Superconducting
Magnetic Levitation
The track are walls with a continuous series of vertical
coils of wire mounted inside. The wire in these coils is
not a superconductor.
As the train passes each coil, the motion of the
superconducting magnet on the train induces a current
in these coils, making them electromagnets.
The electromagnets on the train and outside produce
forces that levitate the train and keep it centered above
the track. In addition, a wave of electric current sweeps
down these outside coils and propels the train forward.
The Yamanashi MLX01MagLev Train

8. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
APPLICATIONS: Medical
The superconducting magnet coils produce a large and
uniform magnetic field inside the patient's body.
MRI (Magnetic Resonance Imaging) scans produce detailed images
of soft tissues.

9. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science
APPLICATIONS: Power
Superconducting Transmission Cable
From American Superconductor
The cable configuration features a conductor
made from HTS wires wound around a flexible
hollow core.
Liquid nitrogen flows through the core, cooling
the HTS wire to the zero resistance state.
The conductor is surrounded by conventional
dielectric insulation. The efficiency of this
design reduces losses.

10. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science

11. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science

12. MMAT 317 Electronic and Magnetic Properties of Materials
CHAPTER 2
Institute of Materials Science