Embed Size (px)
Citation preview
TFA-MOD derived YBa2Cu3O7-x thick films assisted by a high magnetic field
Wang H, Wang Q L, Huang H
Li B L, Ma Y W, Yan L G
Applied Superconductivity Technology Research Division, IEE
CAS
Institute of Electrical Engineering CAS www.iee.ac.cn
Outline
Difficulties in fabrication of thick YBCO film for coated conductors
Offer a new method
Theoretical analyses for feasibility
Institute of Electrical Engineering CAS www.iee.ac.cn
Biaxially textured YBCO coated conductor from epitaxial growth
Metallic substrate
Ceramic buffer layers
YBCO film
Institute of Electrical Engineering CAS www.iee.ac.cn
In situ, eg. PLD, CVD
Ex situ, eg. TFA-MOD
Two kind techniques:
Present level
Application level
Jc
ts
1 MA/cm2
1 MA/cm2
1
m≥5
m
Thickness limitation of epitaxial growth method and application of HMF
Institute of Electrical Engineering CAS www.iee.ac.cn
Non-oriented YBCO grains ∝ ts
c
oriented YBCO grains
Textured buffer layers
J
tstlim
JcJeng
Epitaxial growth techniques (PLD, LPE, TFA-MOD, etc):
tlim≤1.5 m
Hex
t s
High magnetic field assisted TFA-MOD method for thick YBCO film
Institute of Electrical Engineering CAS www.iee.ac.cn
)(5.632)(25222 422
122 gg HFOCuYBaOHOCuYCuOBaF
Metal trifluoroacetate solution
Film coating
Low temperature roasting
High temperature roasting with HMF
3 useful effects of
HMF in theory
Magnetic orientation
Magnetically preferred nucleation
Magnetic interaction
Magnetic orientation of non-oriented YBCO nuclei during chemical reaction
Institute of Electrical Engineering CAS www.iee.ac.cn
7nm liquid layer at the growth interface
(Solovyov, 2000)
Gro
wth
d
irecti
on
Fr.
textu
red
b
uff
er
layer
YBCO:
# Orthorhombic system
# △χc-a ＝ 1.2×10-9 m3/kg (330℃)
# 1030℃, 7T, solidification, ok (Lee et al, 1992)
High T roasting: 850℃, 30min
Magnetically preferred nucleation of YBCO during chemical reaction
0
Institute of Electrical Engineering CAS www.iee.ac.cn
acMG 2
02
1ex
ac H YBCO:
Magnetic refining of YBCO grains during MOCVD on MgO substrate
(Ma Yanwei et al, 2000 )
0T
4T
2T
8T
Magnetic interactions between c-axis oriented YBCO grains
Institute of Electrical Engineering CAS www.iee.ac.cn
20
21
4 l
mmF
cc
I
2
l
HK exI
21
21210
16 aa
VVK
cc
I
Hex
+
+-
-c
c
IF1
2
Two possible effects:
Maintain c-axis texture in thick YBCO film
Densify the thick YBCO film
Conclusions:
When HMF ⊥ Textured substrate The field is of benefit to maintain
high quality c-axis texture so as to be good for biaxial texture in thick YBCO film.
HMF assisted TFA-MOD method is a promising new technique to obtain practical YBCO coated conductors.
Institute of Electrical Engineering CAS www.iee.ac.cn
The experiments are undergoing!
WANG HUI ： 010-6262 6276(O)
010-6254 2034(Fax)
E-mail: [email protected]
Institute of Electrical Engineering CAS www.iee.ac.cn
