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