7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 1/12

SUPERCONDUCTING

CERAMICS

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 2/12

DEFINITION OF TERMS

Critical Temperature , Tc: temperature where a ceramic material becom

superconductive

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 3/12

WHAT IS A SUPERCONDUCTOR?

A material is said to be superconductive if

1. Zero electrical resistivity.

2. ability to expel an applied magnetic eld(the

eissner e!ect".

#n order to attain superconductivity$ most

materials must be cooled to near absolute %ero (&2')* + &,-)/"

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 4/12

SUPERCONDUCTING CERAMICS

0erovsite structure

1: considered as rst superconducting ceramic$oxygen&deecient 3r4i5 (4c6 7.--8"

1': 9a0b7.'-9i7.2-5 (4c6 18" 1: *opper&oxide ceramic discovered by ;.<.

9ednor% and 8.A. =ller$ Lat!aum "ariumC#pper O$i%e$ or >9*5 (4c6 -8"

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 5/12

HIGH TEMPERATURESUPERCONDUCTOR

 4c ? ''8(boiling point of li@uid nitrogen"

*opper&oxide ceramics

#3ABAC4A<D3:

1.  very brittleE

2.  degrade under common environmental inFuences

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 6/12

HIGH TEMPERATURESUPERCONDUCTOR

MATERIAL FORMULA NOTATION TC&'(

 )ttrium "arium C#pperO$i%e

 G9a2*u5'  G12

"i+mut! Str#tiumCalcium C#pper O$i%e

9i23r2*a*u25 9i&2212 7

9i23r2*a2*u5 9i&222 117

T!allium "arium CalciumC#pper O$i%e

 4l2*a29a2*u517  4l&222 12-

Mercur "arium CalciumC#pper O$i%e

Hg9a2*a2*u517 Hg&122 1,

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 7/12

PROCESSING

CON*ENTIONAL-./ MI0ING: 4he appropriate amounts of precursor powders$ usually oxides a

carbonates$ are mixed thoroughly using a 9all mill.

1/ CALCINATION: 4hese powders are calcined in the temperature range from

-7 )* for several hours. 4he powders are cooled$ reground and calcined process is repeated several times to get homogeneous material.

2/ SINTERING: 4he powders are subse@uently compacted to pellets and sint-7 )* in an oxygen atmosphere.

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 8/12

PROCESSING

POWDER3IN3TU"E &PIT( METHOD suited to processing 9i&222

0#4 is not used for G9*5 (Gttrium barium copper oxide" as it does not have the wre@uired to generate ade@uate JtextureJ (alignment" in the 0#4 process

1. A silver or silver alloy is lled with the partially reacted precursor powdersto yield 9i&222

2.  4he tube is then drawn down to a wire 1&2 mm diameter.

.  4he wire is rolled into a tape$ usually with a width&to&thicness ratio of app17:1.

,.  4he composite is then heated to 77&77 )* when the powder partially me

-.  4he recrystalli%ation process is controlled and the pure 9i&222 phase devlarge grains oriented so that *u&5 planes lie parallel to the silver surface

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 9/12

END PRODUCT

 G9*5 93**5

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 10/12

MEISSNER EFFECT

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 11/12

MEISSNER EFFECT

7/17/2019 Superconducting Ceramics

http://slidepdf.com/reader/full/superconducting-ceramics 12/12

APPLICATION