YBa2Cu3O7-delta (YBCO) films with Zr doping have been prepared successfully by the trifluoroacetate metal-organic deposition (TFA-MOD) method through dissolving Zr acetylacetonate into the precursor solution. Yttria-stabilized zirconia(YSZ)nanoparticles were detected in the doped YBCO films by XRD. From the analysis of XRD omega and phi scans, the doped films have better out-of-plane and in-plane textures than those of the un-doped YBCO film. Although the doped YBCO films have lower T-c than that of the un-doped YBCO film, a very significant enhancement of normalized J(c) is displayed as compared to the undoped film at applied fields, indicating that an effective pinning force was created by Zr doping

Liu, Min

Ma, Lin

Shi, Dongqi

Suo, Hongli

Ye, Shuai

Zhao, Yue

Zhou, Meiling

English

Research Online

University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 1-1-2009 YBCO films with Zr4+ doping grown by MOD method Min Liu University of Wollongong, minliu@uow.edu.au Hongli Suo Beijing University of Technology, China Shuai Ye Beijing University of Technology, China Dongqi Shi University of Wollongong, dongqi@uow.edu.au Yue Zhao Beijing University of Technology, China, yue_zhao@uow.edu.au See next page for additional authors Follow this and additional works at: https://ro.uow.edu.au/aiimpapers  Part of the Engineering Commons, and the Physical Sciences and Mathematics Commons Recommended Citation Liu, Min; Suo, Hongli; Ye, Shuai; Shi, Dongqi; Zhao, Yue; Ma, Lin; and Zhou, Meiling, "YBCO films with Zr4+ doping grown by MOD method" (2009). Australian Institute for Innovative Materials - Papers. 253. https://ro.uow.edu.au/aiimpapers/253 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: research-pubs@uow.edu.au YBCO films with Zr4+ doping grown by MOD method Abstract YBa2Cu3O7-delta (YBCO) films with Zr doping have been prepared successfully by the trifluoroacetate metal-organic deposition (TFA-MOD) method through dissolving Zr acetylacetonate into the precursor solution. Yttria-stabilized zirconia(YSZ)nanoparticles were detected in the doped YBCO films by XRD. From the analysis of XRD omega and phi scans, the doped films have better out-of-plane and in-plane textures than those of the un-doped YBCO film. Although the doped YBCO films have lower T-c than that of the un-doped YBCO film, a very significant enhancement of normalized J(c) is displayed as compared to the undoped film at applied fields, indicating that an effective pinning force was created by Zr doping. Keywords YBCO, films, Zr4, doping, grown, MOD, method Disciplines Engineering | Physical Sciences and Mathematics Publication Details Liu, M, Suo, H, Ye, S, Shi, D, Zhao, Y, Ma, L & Zhou, M (2009), YBCO films with Zr4+ doping grown by MOD method, IEEE Transactions on Applied Superconductivity, 19(3), pp. 3403-3406. Authors Min Liu, Hongli Suo, Shuai Ye, Dongqi Shi, Yue Zhao, Lin Ma, and Meiling Zhou This journal article is available at Research Online: https://ro.uow.edu.au/aiimpapers/253 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 19, NO. 3, JUNE 2009 3403YBCO Films With   DopingGrown by MOD MethodMin Liu, Hongli Suo, Shuai Ye, Dongqi Shi, Yue Zhao, Lin Ma, and Meiling ZhouAbstract—   (YBCO) films with Zr dopinghave been prepared successfully by the trifluoroacetate metal-or-ganic deposition (TFA-MOD) method through dissolving Zracetylacetonate into the precursor solution. Yttria-stabilized zir-conia(YSZ)nanoparticles were detected in the doped YBCO filmsby XRD. From the analysis of XRD and scans, the dopedfilms have better out-of-plane and in-plane textures than those ofthe un-doped YBCO film. Although the doped YBCO films havelower  than that of the un-doped YBCO film, a very significantenhancement of normalized  is displayed as compared to theundoped film at applied fields, indicating that an effective pinningforce was created by Zr doping.Index Terms—Nanoparticle doping, TFA-MOD, YBCO film.I. INTRODUCTIONF OR practical applications, especially power applica-tions, high temperature superconductors (HTS) such as(YBCO) need to carry a high critical currentdensity under high magnetic fields. However, due to vortexmotion, the capability of YBCO to carry currents is significantlyreduced at higher applied magnetic fields. There is an effectiveway to improve the in-field performance of coated conductor byintroducing various kinds of pinning centers using a variety oftechniques, including interlayers of non-superconducting mate-rials [1], [2], mixed rare-earth doping [3], [4], and doping withself-aligned (BZO) nanodots and nanorods [5]–[7],as well as the use of nanoparticle-modified substrate surfaces[8], [9]. Among these approaches, BZO nanoparticles [7], [9]grown heteroepitaxially within laser-ablated YBCO films arethe most popular, because these particles are easily incorpo-rated into the films from a source target composed of a ceramicBZO/YBCO mixture. Using a pulsed laser deposition (PLD)process, Goyal [7] et al. have succeeded in producing long,nearly continuous vortex pins along the -axis in YBCO, in theform of self-assembled stacks of BZO nanodots and nanorods,Manuscript received August 16, 2008. First published June 05, 2009; cur-rent version published July 15, 2009. This work was supported by the NationalBasic Research Program 973 of China (2006CB601005), National Natural Sci-ence Foundation of China (50771003), National High Technology Researchand Development Program of 863 (2007AA03Z242) and the program of theFoundation for the Author of National Excellent Doctoral Dissertation of China(200331).M. Liu, H. L. Suo, S. Ye, Y. Zhao, L. Ma, and M. L. Zhou are with the Col-lege of Materials Science and Engineering, Beijing University of Technology,Beijing, 100022 China (e-mail: Lm@bjut.edu.cn).D. Q. Shi is with the Institute for Superconducting and Electronic Materials,the University of Wollongong, NSW 2522, Australia (e-mail: dongqi@uow.edu.au).Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/TASC.2009.2018502which led to an improvement in in magnetic fields. Recently,a new strategy for introducing BZO nanoparticles into YBCOfilms has also been developed by J. Gutierrez et al. [10], [11]on the basis of easily scalable chemical solution depositiontechniques. The random crystalline orientation is the essentialfeature distinguishing chemically prepared nanocompositefilms from those prepared through vacuum deposition methods.The quasi-isotropic character of the pinning has demonstratedthat this new strategy is very effective in preventing vortex mo-tion at high fields and high temperatures for all magnetic-fieldorientations. In this work, epitaxial YBCO/YSZ nanocom-posite thin films were grown from a non-vacuum, low cost,and easily scalable metal-organic deposition method, and theirmicrostructures and physical properties were investigated.II. EXPERIMENTALThe trifluoroacetate precursor solution was preparedby a standard TFA-MOD process with a cation ratio of. A Zr acetylacetonate precursorin stoichiometric proportions was added to obtain the TFAprecursor solution with 6 mol.% Zr doping. The solution wascoated on single-crystal substrates with(001)-orientation by spin coating at a speed of 4000 rpm for2 min at room temperature. The wet films were decomposedto amorphous precursor films by slowly heating them up to400 in a humid oxygen atmosphere. The amorphous pre-cursor film was heated up to 800 in humid (100ppm ) atmosphere and held for 90 minutes. An oxygenationprocess was carried out at 550–450 C for 90 min to achievethe superconducting phase.X-ray diffraction measurements were carried out to examinethe phase of the YBCO films. X-ray -scans and -scans wereused to evaluate the out-of-plane and in-plane textures of theYBCO films, respectively. The film thickness after growthwas determined, by profilometer analysis, to be 250–300nm. The DC magnetization measurements were carried outwith a physical properties measurement system (PPMS) inmagnetic fields parallel to the -axis of the specimens. Thevalues of the YBCO films in magnetic fields were deter-mined by application of the Bean critical state model formula,, where is the verticalwidth of the magnetization hysteresis loop (emu cm ), anda and b (cm) are the cross-sectional dimensions of the sampleperpendicular to the applied field, with .1051-8223/$25.00 © 2009 IEEE3404 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 19, NO. 3, JUNE 2009Fig. 1. (a) X-ray diffraction patterns of undoped YBCO film and YBCO filmswith different doping levels of Zirconium. (b) Enlargement of a section ofFig. 1(a) showing the presence of     impurity.III. RESULTS AND DISCUSSIONA. Analysis and Comparison of PhasesFig. 1(a) shows X-ray diffraction patterns of the un-dopedand doped YBCO films. Only (00l) diffraction peaks of YBCOwere observed, which indicates a well-textured, -axis orientedgrain structure. In order to obtain further information on phases,XRD of the samples was conducted at a very low scan speed.As shown in Fig. 1(b), impurity was detected inboth un-doped and doped YBCO films because of the use ofa Barium-poor starting solution, which is consistent with theresults for K. Nakaoka [12], [13]. They found that highestvalue was not obtained at a Ba/Y molar stoichiometricproportion of 2.0, but at a Ba/Y molar ratio of 1.4–1.6 owing tothe flux pinning of nano-particles of CuO and in theYBCO grains. So, we chose a Ba/Y molar ratio of 1.5 in bothpure and doping YBCO coating solution.We found that Yttria-stabilized Zirconia(YSZ)phase was de-tected in the YBCO films with Zirconium doping, which is notconsistent with other reports [10], [11]. BZO phase was identi-fied in Gutierrez J’s YBCO films by using the YBCO precursorsolution in stoichiometric proportions with 10%BZO doping[10]. However, the concentration of Ba in our experiment ismuch less than stoichiometric proportion to form BZO becauseof both using Barium-poor YBCO solution and only dopingZr salts (not BZO solution) into YBCO solution. So, the de-composition compounds of Zr precursor salt are more difficultto react with Ba compound than with the decomposition com-pounds of excess Y salt to form YSZ phase. From the full-widthat half-maximum (FWHM) of the YSZ (200) and (111) peaksand the Scherrer formula, ; Dc is thesize of the YSZ particle; is 0.15406 nm, which is the wave-length of the characteristic X-ray from a Cu target; B and arethe full-width at half-maximum and the diffraction angle of theYSZ (002) and (110) peaks, respectively.) we estimated that thesize of the YSZ nanodots was in the range of 10–20 nm. Theirdimensions are the order of the coherence length of YBCO, andso they can act as flux pinning centers.B. Analysis and Comparison of TextureX-ray diffraction and scans were collected to determinethe out-of-plane and in-plane alignments of the films, respec-tively. It can be clearly seen from Fig. 2, the FWHM valuesof the and scans for the un-doped YBCO films are 0.98and 1.54 , respectively, which are larger than those of the dopedYBCO film. The poor biaxial texture in the un-doped films mayresult from some impurities which are not epitaxi-ally grown. The content in the doped YBCO films isless than that in the un-doped films so that they have very littleeffect on biaxial textures in the doped YBCO films. Further-more, according to the x-ray patterns in Fig. 1(b), the intensityof the YSZ (111) peak is lower than that of the (200) peak, whilethe theoretical value of the YSZ (111) peak is much higher thanthat of the (200) peak, indicating that the presence of randomlyoriented YSZ nanodots do not destroy biaxial textures in thedoped YBCO films.C. Analysis and Comparison ofThe critical temperature of samples was measured via a phys-ical properties measurement system. As shown in Fig. 3, bothun-doped and doped films have the same transition width. How-ever, the of the doped YBCO film is 1.5 K lower thanthat of the un-doped film. The lowering of in the presence ofthe nanoparticles is consistent with other studies done on PLDYBCO films that were doped with nanoparticles [14]. Thereason for the depressed may possibly be Zr substitutions intoYttrium sites, which are able to locally depress . The furtherresearches are still needed to confirm the accurate reasons of thedepressed .D. Analysis and Comparison ofDevices with YBCO films are usually used at a temperatureof 77 K, so we measured the at 77 K using PPMS. Fig. 4(a)shows the field dependence of at 77 K, with the fieldparallel to the -axis. It can be seen that the 6% Zr doped filmhas a very significant enhancement of normalized values ascompared to the un-doped film for all applied fields, indicatingthat an effective pinning force was created by 6% Zr doping.The overall increase in at all magnetic fields can be moreclearly seen when the magnetic-field dependence of the pinningforce, , is presented, as shown in Fig. 4(b).Although decreases monotonically with increasing field,increases to a maximum value at the field of 0.3 T field,LIU et al.: YBCO FILMS WITH DOPING GROWN BY MOD METHOD 3405Fig. 2. FWHM values of the   scan (a) and  scan (b) for undoped YBCOfilms; FWHM values of the   scan (c) and  scan (d) for doped YBCO films.then slowly decreases during further increase of the appliedfield. of 3.0 GNm in the 6% Zr doped YBCO film,Fig. 3. The  of both doped and un-doped YBCO films.Fig. 4. The field dependence of  (a) and the pinning force (b) at 77 K, withthe field parallel to the -axis.which is a close to 500% enhancement compared with that of theun-doped sample, clearly exemplifies the appealing prospectsfor the present nanocomposite films.IV. CONCLUSIONIn conclusion, we have shown that the metal-organic depo-sition technique can be modified to be used as a cost-effectiveand highly versatile method for introducing nanosized pinningcenters into YBCO films. The TFA-YBCO route with Zr doped3406 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 19, NO. 3, JUNE 2009precursor solutions was utilized to fabricate YSZ doped YBCOfilms through an in-situ crystallization process. Investigationsinto the behavior of the critical current density in magnetic fieldsreveal a strong enhancement of at high magnetic fields in theYBCO film with 6% Zr doping. Pinning centers introduced bychemical solution deposition techniques show enhanced pinningproperties in all magnetic fields.ACKNOWLEDGMENTThe authors thank Prof. S. X. Dou (University of Wollon-gong) for his valuable suggestions in preparing this paper.REFERENCES[1] Q. X. Jia, S. R. Foltyn, P. N. Arendt, and J. F. Smith, “High-tempera-ture superconducting thick films with enhanced supercurrent carryingcapability,” Appl. Phys. Lett., vol. 80, no. 9, pp. 1601–1603, Mar. 2002.[2] S. R. Foltyn, H. Wang, Q. X. Jia, and P. N. Arendt, “Overcoming thebarrier to 1000 A/cm width superconducting coatings,” Appl. Phys.Lett., vol. 87, no. 16, pp. 162505-1–162505-3, Oct. 2005.[3] J. L. MacManus-Driscoll, S. R. Foltyn, Q. X. Jia, H. Wang, A. Serquis,B. Maiorov, L. Civale, Y. Lin, M. E. Hawley, M. P. Maley, and D. 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YBCO films with Zr4+ doping grown by MOD method

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YBCO films with Zr4+ doping grown by MOD method

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