Murat BEKTAŞ Dr. Işıl BİRLİK Dr. Osman ÇULHA Doç. Dr. Mustafa TOPARLI

1. Synthesis and Characterization of BZO doped YBCO Superconducting Films With Different Types of Precursors DOKUZ EYLUL UNIVERSITY DEPARTMANT OF METALLURGICAL & MATERIALS ENGINEERING Murat BEKTAŞ Dr. Işıl BİRLİK Dr. Osman ÇULHA Doç. Dr. Mustafa TOPARLI Supervisor: Prof. Dr. Erdal ÇELİK

2. Content • AIM Of THE STUDY • INTRODUCTION • Superconductivity • TFA-MOD Technique • EXPERIMENTAL STUDIES Characterization of; • YBCO Thin FilmProduction from Oxide Powder • YBCO Thin FilmProduction from Acetate-based Presursor • CONCLUSION

3. 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.

4. SUPERCONDUCTIVITY

5. 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.

6. Tc against time illustrating the remarkable development following the discovery in1986 of the high temperature superconductors.

7. During current flow, Lorentz force acts on vortices. Vortices move and generate electrical resistance Problem Pinning of vortices by non superconducting areas. Solution Dislocation Oxygen vacancies Vortex and Flux Pinning Importance of Flux Pinning for HTS • 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!!! • Crystal defects act as natural pinning centers • Fine precipitates of non-superconducting phases • Dislocations • Oxygen vacancies • Small-angle grain boundaries • Twin boundaries

8. Planar Defects Columnar Defects Point Defects 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 • 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.

9. Copper chains Copper planes Copper planes YBa2Cu3O6 Tetragonal YBa2Cu3O7 Orthorhombic 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.

10. TFA-MOD Schematic illustration of metalorganic deposition using trifluoroacetates (TFA-MOD) for fabricating YBCO superconductors.

11. EXPERIMENTAL STUDIES

12. YBCO Thin Film Preparation Coating (Spin Coating) Heat treatment Characterization Preparation of transparent solution

13. Y(OCOCH3)3 Ba(OCOCH3)2 Cu(OCOCH3)2 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. Schematic illustration of coating solution preparation by YBCO powder. Solution Preparation Dissolve in De-ionized water YBCO oxide powder + propionic acid Sol A Y, Ba and Cu acetates + methanol Sol B Add TFA (CH3COOH) Refining with evaporator Solvent (CH3OH) Blue gel with impurities (H2O, CH3COOH) Coating solution with impurities (H2O, CH3COOH) Refining with evaporator Solvent (CH3OH) Blue gel with solvent (CH3OH) Repeat 0.25 M coating solution Schematic illustration of coating solution preparation by ytrium, barium and copper acetates.

14. Solution Preparation Adding Zr-penthanedionate results in: YBa2-xCu3O7-δ + x(BaZrO3) X= 0.006, 0.012, 0.018 (corresponds 6, 12 and 18 mol% BaZrO3)

15. Rotating 6000rpm, 6000 rpm s-1 Application of precursor solution on STO Evaporation of solvent with spin speed substrate All process takes place in a dry nitrogen atmosphere at -25 ˚C dew point. Wet O2 Dry O2 Wet N2+100 ppm O2 Dry O2 Crystallization Oxygenation Pyrolysis • Heat Treatment Process • Spin Coating

16. 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

17. Solution Characterization • Viscosity and Contact Angle

18. Solution Characterization • DTA-TG Sol B Sol A • 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 .

19. (002) YBCO (003) YBCO (100) STO (004) YBCO (007) YBCO Intensity (a.u.) F-A3 F-A2 F-A1 F-A0 2-Theta (Co Kα radiation) Characterization of YBCO Films • XRD F-A series F-B series F-B3 F-B2 F-B1 F-B0 • 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. • (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.

20. Characterization of YBCO Films • SEM F-A series F-B series (a) (b) (a) (b) (c) (c) (d) (d) Surface morphologies of (a) F-A0, (b) F-A1, (c) F-A2 and (d) F-A3 films. Surface morphologies of (a) F-B0, (b) F-B1, (c) F-B2 and (d) F-B3 films.

21. Characterization of YBCO Films • Tc (Critical Temperature) F- A series F- B series 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.

22. Characterization of YBCO Films • 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

23. 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.

24. Thanks for your attention… ACKNOWLEDGEMENT TO; TUBITAK-109M054 Leibniz Enstitute For Solid State and Materials Research Dresden