Murat BEKTAŞ Dr. Işıl BİRLİK Dr. Osman ÇULHA Doç. Dr. Mustafa TOPARLI
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Transcript of Murat BEKTAŞ Dr. Işıl BİRLİK Dr. Osman ÇULHA Doç. Dr. Mustafa TOPARLI
SYNTHESIS AND CHARACTERIZATION OF BZO DOPED YBCO SUPERCONDUCTING FILMS WITH DIFFERENT TYPES
OF PRECURSORS
Murat BEKTAŞ
Dr. Işıl BİRLİKDr. Osman ÇULHADoç. Dr. Mustafa TOPARLISupervisor: Prof. Dr. Erdal ÇELİK
DOKUZ EYLUL UNIVERSITY
DEPARTMANT OF METALLURGICAL & MATERIALS ENGINEERING
Content
AIM Of THE STUDY
INTRODUCTION Superconductivity TFA-MOD Technique
EXPERIMENTAL STUDIES Characterization of;
YBCO Thin Film Production from Oxide Powder YBCO Thin Film Production from Acetate-based Presursor
CONCLUSION
AIM OF THE STUDY • TFA-MOD process using highly purified metal acetates as starting
materials are rather expensive and thus it is desirable to find more economic route.
• Recently, several attempts to use oxide powders such as commercially available REBCO powder as starting materials have been reported which showed comparable Jc (critical current density) for the YBCO films.
• In this study, two different types of BaZrO3 doped YBa2Cu3O7-δ (YBCO) superconducting thin films were prepared using commercially available YBCO powder and yttrium, barium and copper acetate on SrTiO3 (STO) substrates by TFA-MOD method.
• The effect of precursor type on the film structure and superconducting properties were studied.
SUPERCONDUCTIVITY
Superconductivity was first discovered in 1911 by the Dutch physicist, Heike Kammerlingh Onnes. He discovered that the electical resistance goes to zero when mercury is cooled at about 4.2K.
Tc against time illustrating the remarkable development following the discovery in 1986 of the high temperature superconductors.
During current flow, Lorentz force acts on vortices. Vortices move and generate electrical resistance
Problem
Pinning of vortices by non superconducting areas.
Solution
Power applications and high field applications Nuclear magnetic resonance (NMR) Superconducting magnetic energy storage (SMES) HTS conductors need to possess a high critical current density under high magnetic fields.
Improving the in-field Jc has been a topic of enormous technological
importance!!!
Importance of Flux Pinning for HTS
Crystal defects act as natural pinning centers
Fine precipitates of non-superconducting phases Dislocations Oxygen vacancies Small-angle grain boundaries Twin boundaries
Dislocation Oxygen vacancies
Vortex and Flux Pinning
Artificial Pinning Centers
Types of defects such as Y2BaCuO5 inclusions or the introduction of random BaMeO3 (Me:
Mn, Zr, Ir, Hf, ...) nanoparticles.
By building up a layered distribution of a second phase such as Y2BaCuO5 or Y2O3 using a
multilayer deposition.
Process induced modifications with excess yttrium, and decoration of substrate surfaces by nanoscaled particles.
Types of Defects
Point Defects Columnar Defects Planar Defects
Defects need to be of similar size as the coherence length
Coherence length in HTS are on the order of nanometers. So, nanoparticles are necessary.
Compatibility of the nano-structure with superconductor is required.
YBCO (YBa2Cu307-x)
•The compound YBa2Cu307-x,
sometimes called YBCO or Y-123
compound, in its orthorhombic
form is a superconductor below
the transition temperature
Tc =92 K.
•YBCO has perovskite structure.
The structure of YBa2Cu3O7-x.
YBa2Cu3
O6 Tetragon
al
YBa2Cu3O7
Orthorhombic
Copper
chains
Copper
planes
Copper
planes
TFA-MOD
Schematic illustration of metal organic deposition using trifluoroacetates (TFA-MOD) for fabricating YBCO superconductors.
)(325.0
)(3)(2)(
2232
232232332
zyx FOmCnCOCuOBaFOY
CCFOCuCCFOBaCCFOY
)(4225.0 7322232
2
gHFOCuYBaOHCuOBaFOY x
O
EXPERIMENTAL STUDIES
YBCO Thin Film Preparation
Preparation of transparent solution
Coating (Spin Coating)
Heat treatment
Characterization
Schematic illustration of coating solution preparation by ytrium, barium and copper acetates.
Y(OCOCH3)3
Ba(OCOCH3)2
Cu(OCOCH3)2
Dissolve in De-ionized water
Add TFA (CH3COOH)
Refining with evaporator
Blue gel with impurities
(H2O, CH3COOH)
Coating solution with impurities (H2O,
CH3COOH)
Refining with evaporator
Blue gel with solvent (CH3OH)
0.25 M coating solution
Solvent
(CH3OH)
Solvent
(CH3OH)
Schematic illustration of coating solution preparation by YBCO powder.
YBCO powder (Alfa Aesar %99,9)
Dissolve in a mixture of
propionic acid and TFA (8:1)
Magnetic stirrer at 120°C
Refine with evaporator
Sticky, dark blue gel
Adjust the final concentration to 0.25M with a mixture of propionic acid:acetone =1:3.
Repeat
Solution PreparationYBCO oxide powder + propionic acid Sol A Y, Ba and Cu acetates + methanol Sol B
Solution Preparation
PrecursorsName of Solution
Doped-BZO concentration (mol%) Name of Films
YBCO powder
SolA0 0 F-A0
SolA1 6 F-A1
SolA2 12 F-A2
SolA3 18 F-A3
Yttrium, Barium and
Copper acetates
SolB0 0 F-B0
SolB1 6 F-B1
SolB2 12 F-B2
SolB3 18 F-B3
Adding Zr-penthanedionate results in:
YBa2-xCu3O7-δ + x(BaZrO3)
X= 0.006, 0.012, 0.018
(corresponds 6, 12 and 18 mol% BaZrO3 )
0
100
200
300
400
500
600
700
800
0 200 400 600 800 1000
Time (min.)
Tem
pera
ture
(o C
)
Pyrolysis Cry
sta
lliz
ati
on
Oxygenation
Dry
O2
Wet O2
We
t N
2+1
00
pp
m O
2
Dry O2
Characterization of Solutions & YBCO Films
Solution characterization;• Viscosity and contact angle,• DTA-TG (Differential Thermal Analysis-Thermal Gravimetric Analysis),
YBCO film characterization;• XRD (X-Ray Diffractometer), • SEM (Scanning Electron Microscopy)
Physical properties ;• Inductive Tc measurement
• Inductive Jc measurement
Solution Characterization
Solution Name
Viscosity m(Pa.s)
Contact Angle (o)
Sol A0 7.80
22.26Sol A1 6.99
Sol A2 24.72
Sol A3 87.49
Sol B0 4.12
21.28Sol B1 4.76
Sol B2 4.64
Sol B3 4.30
Viscosity and Contact Angle
DTA-TGSolution Characterization
Sol A Sol B
Below 200 oC: Evaporation and release of acetic acid and gel network water.
233 oC: Large loss in mass, combustion reaction due to the presence of acetate groups and loss of TFA, initial formation of BaF2 and CuO phases.
275 °C: Formation of a yttrium intermediate as Y2O3 .
Final combustion: Release of relatively large quantity of CO and CO2 .
Characterization of YBCO Films
2-Theta (Co Kα radiation)
Inte
nsi
ty (
a.u
.)
F-A0
F-A1
F-A2
F-A3
(002)YBCO
(004)YBCO (007)
YBCO
(003
) Y
BC
O(1
00)
ST
O
XRDF-A series F-B series
(00l) reflections of the YBCO phase and (100) STO substrate indicate that the YBCO film has a strong c-axis texture. (004) and (007) orientations of YBCO are lower than
expected for a textured structure.
Major peaks (00l) YBCO and (h00) substrate. BZO (200) peak intensities increases slightly
with increasing BZO concentration. (103) orientation of YBCO is observable, peak
intensity decreases as the BZO concentration increases.
F-B3
F-B2
F-B1
F-B0
Characterization of YBCO Films
(a)
(d)(c)
(b)
Surface morphologies of (a) F-A0, (b) F-A1, (c) F-A2 and (d) F-A3 films.
(a) (b)
(d)(c)
Surface morphologies of (a) F-B0, (b) F-B1, (c) F-B2 and (d) F-B3 films.
SEMF-A series F-B series
Characterization of YBCO Films
Resistivity vs. temperature and Dependence of critical temperature Tc and transition width
ΔTc on the amount of BZO concentration graphs doped and undoped YBCO films prepared from Sol A and Sol B.
Tc (Critical Temperature)
F- A series
F- B series
Characterization of YBCO Films
0 6 12 18
0.0
0.5
1.0
1.5
2.0
2.5
1.42
1.21
1.43
0.97
0
0.74
2.1
Jc
(MA
/cm
2)
BaZrO3 concentration (mol %)
F- A F- B
1.29
Jc (Critical Current Density)
Dependence of inductively measured critical current density Jc on the amount of BZO concentration graph for YBCO films prepared from Sol A & Sol B
Conclusion
YBCO superconducting thin films were successfully prepared from YBCO
powder and yttrium, barium, copper acetate precursors via TFA-MOD method
on STO single crystal substrates and BZO was incorporated into the
structures of them as artificial pinning centers.
According to SEM images, YBCO films prepared from SolA exhibit better
surface morphology and all of them are generally formed by c-axis oriented
grains. BZO doped YBCO films present a denser surface structure with
decreasing porosity compared with the undoped YBCO films. On the other
hand, 18 mol% BZO doped sample surface possesses bigger sized grains in
comparison to the fine grains of 6 and 12 mol% BZO doped sample surfaces.
As a result of Jc measurements, 6 mol% BZO doped YBCO sample prepared
from SolA (YBCO powder) has the highest Jc value.
Thanks for your attention…
ACKNOWLEDGEMENT TO;
TUBITAK-109M054
Leibniz Enstitute For Solid State and Materials Research Dresden