Texture Analysis of Superconducting Films Based on YBCO System

Jourmal of University of Science and Technology BejingVol. 7(2000), No.2, p.107MaterialsTexture Analysis of Superconducting Films Based on YBCO SystemNan Chen'2, Weimin Mao'1) Material Science and Engineering School, University of Science and Technology Bejing, Befing 100083 China2) Department of Materials Science and Engineering. University of Petroleum, Beijing 102200 China(Received 000-04-10)Abstract: Textures in diferent layers of superconductors based on YBCO system are analyzed using the methods ofpole figure and con-ventional φ scans. It is shown that the φ scanning technology has only 1-dimensional description and could omit some information 03-dimensional orientation dstribution, which will influence the superconductor quality. The pole figure method, in contrast, demonstra-tes the orientation dstributio 2dimensionally and gives a comprhensive vicw of thin flm texture, which is a much better method fortexture analysis in superconducting films, in which there is commonly an unique high sharpness texture component.Key words: superconductor, thin film texture; YBCO; pole figureThe critical current density of high temperature(figure 1a)), while the accompanying twinning orien-superconductors depends strongly on grain boundarytations [4] appear besides the cube texture in the othermisorientations [1]. Therefore, one of the purposes ofnickel tape (igure 1()). Figure 2 gives the results ofthe corresponding fabrication process is to obtain high-φ scans for nickel, CeO, YSZ and YBCO respectively,ly textured superconductors, in which only very lowwhich forms a multilayer structure. According to theangle boundaries exist. Long and flexible superconduc-analysis of中scans, the epitaxial N/CeO/YSZ/YBCOting tapes based on YBa,Cu;O (YBCO) are generallystructure should have a good crystallographic align-fabricated by epitaxial deposition on biaxially texturedment.metals [1]. The tapes have commonly 4 layers, ie, Cu-Figure 3 shows the φ scan and the (226) pole figurebic nickel, tetragonal CeO and yttia stabilized ZrO2(YSZ), as well as orthogonal YBCO [2] in the deposi-(a)RDtion order. There should be a crystallographic coherentrelationship between the layers, which maintains thesharp cube texture initialed ftom the nickel substrate, ortransforms the sharp texture in to next layer, where another sharp texture forms. The texture of different layers should be frequently determined during the fabrica-tion process, in order to insure the tape quality. Howo◎ever, the D scanning technology is a conventionalmethod for the quality control [3], which might inducesome problems, and should be modified.(b)1 Experiment and Results{111} incomplete pole figures of two high puritynickel tapes were determined. During the fabricationprocess of a superconducting tape. the φ scanning me-asurement was carried out by means of {111}, (202)，中国煤化工(202) and (226) diffraction of nickel, CeO2, YSZ andHCNMHGYBCO layer, respectively. An incomplete (226) polefigure and the corresponding (226) φ scan of a finalYBCO layer were also determined. All the measure-ment was conducted by X-ray diffraction technology.Figure 1 Texture in nickel substracts, 111} pole figure; den-sity levels: 1, 2, 4, 7, 10, 15 and 20; the maximum values areOne nickel tape has an unique strong cube texture(a) 21.2 and () 10.8 respectively.108J. of Univ. of Sci. and Tech. Beijing, 7(2000), No.28006000 [a)Nb)CeO600营400004002000200100300中10)icYSZYBCO150i 1050中1(0)φ1(°)Figure2中scans. Nickel 111}, CeO; (202), YSZ (202) and YBCO (226).5000[100] texture indicated in the (226) pole figure (igure3(b)-2 Discussion5 3000φ scans give very useful information about orienta-tion distribution of superconducting tapes. However,the information is uncompleted. The perfect orientation1000distribution of CeO and YSZ is schematcally shownin figure 4(a) in the format of (202) pole figure. Thecorresponding orientation distribution is also schemati-cally shown in figure 4(b) in the format of {111} poleφ/()figure for the nickel tape and in the format of (226) pole(bfigure for YBCO layer. The orientation distributionsobtained by φ scans are the distribution of orientationdensities indicated by the full circle lines in figure 4. Itis clear, therefore, that the φ scans do not contain com-plete information of the layer textures.Initialing from the nickel texture shown in figure 1(a) and appropriate fabrication technology, an excellent IYBCO layer can be produced with very high criticalcurrent中国煤化工layer should not Sogood iY片C N M H Sstarted from the nieFigure 3中Scan (a) and 226) pole figure b) of a YBCO layerkel texture SIOWI m ugune TUp 1 can be seen, accord-ing to figure 4(b), that the obvious texture difference in-of the final YBCO layer. The φ scan indicates a gooddicated in figure 1 will be neglected by中scans, afterdensity distribution (figure 3(a)), while some other tex-which a very similar density distributions in the case ofnure components are also observed besides the (001)figure l(a,b) will be obtained in the φ scans.N. Chen, W. Mao:109(a)(b)Figure 4 Positions of φ scans in the corresponding pole figures. a) Ni (202) and YZS (202), (b) Ni 11} and YBCO (226).The full width of half maximum of the difractionYBCO system are examined and compared by the polepeaks in the中scanning curves [3, 5] is commonly me-figure and中scan. It is indicated that the中scan aloneasured or calculated using ftting treatment. It is be-could not give a complete texture description of the lay-lieved that the epitaxy will be excellent in the case thaters. The pole figure measurement should also be used,[3, 5]: (1) the peaks are strong enough, (2) the widthsto determine the texture quality of the superconductingare rather low and similar among the φ scans from dif-films.ferent layers, and (3) no other peaks are observed in theReferencesφ scans besides those expected (figures 2 and 4).[1] A. Goyal, D.P. Norton, et al. : Appl Phys. Lett, 69(1996), p.Figure 3 demonstrates that the φ scan can really omitother texture information except the expected one. The[2中国煤化工evlopment of Baxialyφ scan in figure 3(a) could express that the YBCO lay-YHC N M H Glled-Ni Substrates for Higher is pretty good since no unexpected peaks are ob-Current YBa0sOz Loateo Conductors. [in] ISS'96 Proceed-served in the φ scans, though it is not really so.ings. Sapporo, Japan, 1996, p.1.[3] D. P. Norton, A. Goyal, et al. : Science, 2740 1996), p.755.3 Conclusions[4] w. Mao: J. Mat. Eng. & Perf, 8( 999), p.556.[5] x. M Xiong, Y. L. Zhou, et al: Physica C, 298(1998) p.178.The textures of superconducting films based on