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Superconducting Ceramics
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7/17/2019 Superconducting Ceramics
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SUPERCONDUCTING
CERAMICS
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DEFINITION OF TERMS
Critical Temperature , Tc: temperature where a ceramic material becom
superconductive
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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')* + &,-)/"
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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"
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HIGH TEMPERATURESUPERCONDUCTOR
4c ? ''8(boiling point of li@uid nitrogen"
*opper&oxide ceramics
#3ABAC4A<D3:
1. very brittleE
2. degrade under common environmental inFuences
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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,
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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.
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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
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END PRODUCT
G9*5 93**5
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MEISSNER EFFECT
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MEISSNER EFFECT
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APPLICATION