synthesis and characterization of ybco and …janna mateeva, anna staneva, boris martinov, blagoy...

Janna Mateeva, Anna Staneva, Boris Martinov, Blagoy Blagoev, Timur Nurgaliev

1215

SYNTHESIS AND CHARACTERIZATION OF YBCO AND YBCO/Ag SUPERCONDUCTING CERAMIC COMPOSITES

CONTAINING REDUCED GRAPHENE OXIDE

Janna Mateeva1, Anna Staneva1, Boris Martinov1, Blagoy Blagoev2, Timur Nurgaliev3

ABSTRACT

The high-temperature ceramic superconductors and nanomaterials are among the most promising groups of materials that are intensively studied. Graphene is a new material with unique electrical, optical and biological properties. The high mobility of graphene charges implies the possibility of using it as a suitable additive improving the superconductors’ physical characteristics. The idea of this study is to synthesize series of bulk composites based on YBCO superconductors, silver and RGO with superconducting properties. The YBCO phase is obtained by a ce-ramic technology. It includes Ag aiming better sintering. Graphene is synthesized by a modified Hammer’s method. XRD is applied to verify the obtaining of the starting phases. The synthesized composites are characterized by XRD, SEM and EDX analysis. All composites prepared are superconductive and have a Meissner effect.

Keywords:Superconducting materials, YBCO, reduced graphene oxide, composites, synthesis, phaseformation.

Received 12 June 2019Accepted 16 August 2019

Journal of Chemical Technology and Metallurgy, 54, 6, 2019, 1215-1222

1University of Chemical Technology and Metallurgy 8 Kliment Ohridski, 1756 Sofia, Bulgaria E-mail: [email protected] Institute of Solid State Physics Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee 1784 Sofia, Bulgaria3 Institute of Electronics, Bulgarian Academy of Sciences 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria

INTRODUCTION

One of the main topics of modern sciences (physics, chemistry, material science) refers to the study of super-conducting materials. The main problem faced is the synthesis of new ceramic superconductors with a high critical transition temperature and an increase of their density, mechanical strength and chemical resistance. A solution would be to study different additives effect on the phase formation, the structure and the properties of the superconducting materials.

Y-Ba-Cu-O system is one of the most intensively investigated [1 - 5]. Especially important is the finding attributed to the high temperature superconductivity at

Tc = 70 K - 98 K observed in a whole series of ceramic materials of the general formula of ReBa2Cu3O7-d, where Re = Y, La, Nd, Sm, Eu, Gd, Ho, Er, Lu. The classical ceramic technology is the most commonly used synthesis method. It refers to homogenizing and grinding of the corresponding amounts of the initial oxide components, firing in air at 930°C and slow cooling [6 - 8].

One of the basic methods of superconducting ce-ramic modification requires the use of specific additives aiming to improve the superconductive parameters, to optimize the technological conditions of synthesis, to increase the ceramic density, to achieve an appropriate microcrystalline orientation, to improve the mechanical strength and the chemical resistance [9 - 11].

Journal of Chemical Technology and Metallurgy, 54, 6, 2019

1216

The previous research of our team has been focused on the synthesis of superconductive YBCO ceramics con-taining silver. The presence of silver determines different effects connected with the increase of the critical tem-perature (Tc) and the critical current density, the decrease by 50°C of the melting temperature, the stimulation of the grain growth of 123 YBCO phase and the improvement of the mechanical properties observed [12, 13].

On the other hand, graphene is a new material of unique electrical, optical and biological properties [14 - 16]. The high mobility of graphene charges implies the possibility of using it as a suitable additive aim-ing improvement of the physical characteristics of the superconductors and production of materials of electri-cally conductive properties at temperatures above that of Tc. The applications of graphene are very promising as it has many interesting mechanical [14], thermal [15] and electric properties [16]. The superiority of graphene and composites on its basis in respect to the traditional materials is verified by a number of studies [17 - 19]. Our team has investigated composites based on RGO containing different components [20 - 22].

So far, there are single studies on the synthesis of YBCO composites with graphene participation [23 - 28].

The aim of this study is the synthesis and the struc-tural characterization of three series of compositions of new superconducting YBCO composites containing Ag and RGO. The content of RGO is assumed to amount to 1 mass %, 2 mass %, 5 mass %, 10 mass % and 20 mass %. The effect of RGO on the composites superconduct-ing properties has to be also identified.

EXPERIMENTAl

YBCO ceramic and reduced graphene oxide (RGO) were separately synthesized in the course of the composite materials production. The high temperature superconductive YBCO ceramics was obtained by the most popular classic ceramic technology. 3 series of YBCO compositions – pure YBCO (Y), YBCO + 5 % Ag (5Y) and YBCO + 10 % Ag (10Y) (Table 1) were synthesized. Y2O3, BaCO3, CuO, AgNO3 were used as initial compounds. The stoichiometric amounts of the oxides and the carbonates used were mixed and grinded

in an agate mortar. The fine mixtures were tableted using PVA plasticizer and a press with a pressure of 5 t. The tablets were fired initially at 450° C for 2 h for burning of the plasticizer and then at 930°C for 16 h in air.

RGO was obtained by oxidation and reduction of a graphite powder. The first step referred to the synthesis of graphene oxide (GO) through a modified Hummers method [29] using a graphite powder (Alfa Aesar 99.9 %, 20+84 mesh). The graphite was subjected to intensive mechanical treatment using a planetary ball mill (Fritsch – Pulverisette) with balls made of zirconium dioxide. The rotation speed was equal to 500 rpm, while the grinding time amounted to 1 h. This step was followed by oxidation of the milled graphite powder (10 g) which was mixed with 200 ml of H2SO4 and 50 ml of H3PO4. The mixture was stirred vigorously in an ice bath for 40 min. 30 g KMnO4 were added slowly to avoid the increase of the reaction mixture temperature. 460 ml of distilled water were added dropwise after stirring in the course of 30 min. The resulting suspension was left to stand for 18 h. Then a solution of 50 ml of 30 % hydrogen peroxide in 700 ml of distilled water was added dropwise at constant stirring at a room tempera-ture. After stirring for 1 h, the suspension was washed with 1M HCl and several times with deionized water. The resulting graphite oxide was dried for 12 h at 70°C. The exfoliation of the graphite oxide to GO sheets was performed by sonication of the graphite oxide suspension for 2h using the ultrasonic processor Bandelin Sonorex (35 KHz, 240W). The reduced graphene oxide (RGO) was prepared by GO reduction. Sodium borohydride was used as a reducing agent. The common proportions were as follows: 0.2 g of GO, 2.0 g of NaOH and 2 g of a reducing agent (sodium borohydride) in 100 ml of deionized water. The mixtures were stirred at a room temperature for 24 h. The resulting RGO materials were washed several times with deionized water and dried for 12 h at 70°C.

The synthesis of the superconducting composites required the addition of 1 mass %, 2 mass %, 5 mass %, 10 mass % and 20 mass % of RGO (Table 1) to all three ceramic superconductors (YBCO, YBCO + 5 mass % Ag, YBCO + 10 mass % Ag). The resulting mixtures were homogenized in an agate mill, dissolved in alcohol


1217

and then subjected to sonication for 2h using Sonorex ultrasonic processor. The resulting suspensions were evaporated and dried in a laboratory drier at 90° C for 10 h. The powders were subjected to XRD, SEM, EDX analysis. The tablets were formed using a 7 t pressure hydraulic press. They were tested for a Myssner effect. This required the cooling of the tablets to a temperature below the critical one using liquid nitrogen in presence of an external magnetic field. Levitation of the supercon-ducting composites above the magnet was also observed.

All samples obtained were characterized by powder XRD using Bruker D8 Advance powder diffractometer with Cu Kα radiation and a LynxEye detector. The data collection was performed in the range of 10°2θ to 90°2θ with a step of 0.03°2θ and counting time of 57 s/step. The sample was rotated at 15 rpm. Diffracplus EVA and ICDD-PDF2 (2014) database was used for the phase composition identification.

SEM and EDX analyses of RGO, YBCO, YBCO/Ag and YBCO/graphene composites was performed on SEM/FIB LYRA I XMU microscope by TESCAN (Electronic source: tungsten heater; Resolution - 3.5 nm at 30 kV; Acceleration voltage - 200 V to 30 kV;

EDX detector: BRUKER’s Quantax 200; Spectroscopic resolution at Mn-Ka and 1 kcps of 126 eV).

RESUlTS AND DISCUSSION

The XRD patterns show specific peaks for YBCO superconductor, Ag and RGO. Fig. 1 illustrates the XRD patterns of the initial compounds – pure YBCO (Y), YBCO + 5 % Ag (5Y) and YBCO + 10% Ag (10Y). The XRD pattern of RGO is shown in Fig. 2. The presence of the superconducting orthorhombic YBa2Cu3O7-d, phase, Y2Ba1Cu1O6-d phase and Ag in composites with participa-tion of 5 mass % and 10 mass % Ag is demonstrated.

Table 1. Series of compositions containing YBCO, Ag and RGO.

Fig. 1. XRD patterns of the initial compounds – pure YBCO, YBCO + 5 % Ag and YBCO + 10 % Ag.

Fig. 2. XRD patterns of RGO.

Designation Composition Y YBCO

Y1 YBCO + 1 mass % RGO Y2 YBCO + 2 mass % RGO Y5 YBCO + 5 mass % RGO

Y10 YBCO + 10 mass % RGO Y20 YBCO + 20 mass % RGO

5Y YBCO + 5 mass % Ag

5Y1 YBCO + 5 mass % Ag + 1 mass % RGO 5Y2 YBCO + 5 mass % Ag + 2 mass % RGO 5Y5 YBCO + 5 mass % Ag + 5 mass % RGO

5Y10 YBCO + 5 mass % Ag + 10 mass % RGO 5Y20 YBCO + 5 mass % Ag + 20 mass % RGO

10Y YBCO + 10 mass % Ag

10Y1 YBCO + 10 mass % Ag + 1 mass % RGO 10Y2 YBCO + 10 mass % Ag + 2 mass % RGO 10Y5 YBCO + 10 mass % Ag + 5 mass % RGO

10Y10 YBCO + 10 mass % Ag + 10 mass % RGO 10Y20 YBCO + 10 mass % Ag + 20 mass % RGO


1218

The XRD patterns of YBCO/Ag/RGO composites are demonstrated in Figs. 3 - 5. The presence of the superconducting phase YBCO, Ag and RGO in the composites is verified. Fig. 3 shows the presence of the orthorhombic superconducting phase YBa2Cu3O7-d, and Y2Ba1Cu1O6-d phase in the composite containing 5 % RGO. The intensity of the peaks corresponding to these two phases is significantly decreased, which could be attributed to the reduction of the crystals size as a result of the applied ultrasonic treatment in the course of the composite synthesis with the participation of 5 % RGO.

Very good crystallisation of the orthorhombic super-conducting phase YBa2Cu3O7-d is observed in case of Ag addition to YBCO and RGO-containing composites. The amount of Y2Ba1Cu1O6-d phase is significantly decreased (Fig. 4). The X-rays patterns show the presence of silver in all samples, as well as RGO peaks in the spectra of the composites containing 5 mass % and 10 mass % RGO.

With the addition of 10 mass % Ag to YBCO very good crystallization of the orthorhombic superconduct-ing phase YBa2Cu3O7-d is also observed (Fig. 5). The silver peaks intensity increases significantly. The X-ray diffraction patterns of RGO composites also detect peaks corresponding to RGO phase.

Microstructural observation and chemical analysis were performed on superconducting ceramics by a scanning electron microscope (SEM) equipped with a dispersive energy system of emitted X rays (EDX).

The SEM and EDX analyses of YBCO/Ag/RGO composites are presented in Figs. 6 - 12. The EDX analy-

Fig. 3. XRD patterns of YBCO and YBCO/RGO com-posites.

Fig. 4. XRD patterns of composites YBCO + 5 mass % Ag and YBCO/5 mass % Ag/RGO.

Fig. 5. XRD patterns of composites YBCO + 10 mass % Ag and YBCO/10 mass % Ag/RGO. Fig. 6. SEM images of YBCO superconducting phase.

YBCO


1219

Fig. 7. SEM and EDX analysis of composite YBCO and 1 mass % RGO.

Fig. 8. SEM and EDX analyses of composite YBCO and 5 mass % RGO.

Fig. 9. SEM and EDX analysis of composite YBCO and 5 mass % Ag.

Fig. 10. SEM and EDX analysis of composite YBCO and 5 mass % Ag + 1 mass % RGO.

RGO

YBCO


1220



ses of all composites show the distribution of Y, Ba, Cu and O elements, which corresponds to the stoichiometric ratio of the superconducting phase YBa2Cu3O7-d (Figs. 7-12). The EDX analysis of composite YBCO and 5 mass % Ag shows a small increase of silver in the mid-dle of the grain whereas the amount of silver is sharply raised near the edge of the grain. The EDX results reveal that the elements used for the preparation of samples are distributed homogeneously and the Ag atoms are inluded into the crystal structure.

The silver particles are located along the YBCO crystallites‘ edges. It is also demonstrated by the dis-tribution of the elements in the EDX analyses (Fig. 9).

SEM images show the surface morphology and grain connectivity in the sample and those of a high magnification of the composites containing RGO show the presence of graphene flakes (Figs. 8 and 12).

The EDX analyses of the elements distribution of all composites containing RGO demonstrate the presence of

carbon in an amount corresponding to the compositions of the respective composites (Figs. 7, 8, 10-12).

Study on the superconducting properties of the composites will be presented in a future work.

CONClUSIONS

Three series of graphene composites based on pure YBCO superconducting phase, YBCO + 5 mass % Ag and YBCO + 10 mass % Ag are synthesized varying the RGO content (1 mass %, 3 mass %, 5 mass %, 10 mass % and 20 mass % for each series). The participation of the superconducting phase YBCO, Ag and RGO in all composites is verified through XRD, SEM and EDX analyses. It is shown that the addition of silver to YBCO superconductive ceramics facilitates the synthesis of the orthorhombic superconducting phase YBa2Cu3O7-d at the expense of the concomitant phase Y2Ba1Cu1O6-d improving the sinthering and the contact between the

40 000x

RGO


1221

grains of the superconductive phase. The SEM analyses demonstrate the even distribution of the graphene layers throughout the bulk composite material. All composites cooled in liquid nitrogen are characterized by a Meissner effect, which proves that the addition of RGO to the superconducting YBCO phase does not interfere with its superconductive properties.

AcknowledgementsThis study has been financially supported by Na-

tional Programme “Young Scientists and Postdoctoral Researchers” and Contract KП-06-H27/17, 18.12.2018, National Science Fund of Ministry of Education and Science of Bulgaria.

REFERENCES

1. J.G. Bednorz, K.A. Muller, Possible high Tc super-conductivity in the Ba-La-Cu-O system, Phys. B, 69, 1986, 189-193.

2. H. Maeda, Y. Tanaka, M. Fukutomi, T. Asano, A new high-rc oxide superconductor without a rare earth element, Japan. J. Appl. Phys., 27, 1988, 209-210.

3. C.N.R. Rao, Synthesis of cuprate superconductors, Supercond. Sci. Technol., B51, 6, 1993, 1-22.

4. N.E. Alekseevskii, G.M. Kuzmicheva, E.P. Khlybov, et al., Superconducting Phases with Perovskite-Related Structures, Pisma Zh. Eksp. Teor. Fiz., 48, 1, 1988, 45-47, (in Russian).

5. R.J. Cava, Oxide superconductors, J. Am. Ceram. Soc., 83, 2000, 5-28.

6. S.S. Michael, N.A. Mukhlif, Superconductivity and Structure of Ceramic YBa2Cu3 - xAgxO7, Mater. Res.Bull., 23, 12, 1988, 1879-1903.

7. S. Jin, E. Graebner, Processing and fabrication tech-niques for bulk high -Tc superconductors. A critical review, Mat. Sci. and Eng., B7, 1991, 243-260.

8. T.M. Green, M. Akinc, Shape Forming of Supercon-ducting Ceramics, Am. Ceram. Soc. Bull., 70, 7, 1991, 1162-1166.

9. P. Paturi, J. Raittila, J.-C. Grivel, H. Huhtinen, B. Seifi, R.Laiho, N.H. Andersen, Preparing supercon-ducting nanopowder based YBCO/Ag tapes, Physica C, 372-376, 2002, 779-781.

10. Th. Hopfinger, R. Viznichenko, G. Krabbes, G. Fuchs, K. Nenkov, Joining of multi-seeded YBCO melt-textured samples using YBCO/Ag composites as welding material, Physica C, 398, 2003, 95-106.

11. E. Mendoza, T. Puig, E. Varesi, A.E. Carrillo, J. Plain, X. Obradors, Critical current enhancement in YBCO-Ag melt-textured composites: influence of microcrack density, Physica C, 334, 2000, 7-14.

12. Е.S. Vlakhov, V.T. Kovachev, M. Polak, M. Majoros, Y.B. Dimitriev, S. Jambazov, E. Kashchieva, A. Staneva, The influence of Ag and Te additions on the magnetization of hollow cylinder YBCO ceramics, Physica C, 175, 1991, 335-341.

13. E. Vlakhov, E. Gattef, Y. Dimitriev, A. Staneva, Syn-thesis and superconductivity of YBa2Cu3Oy ceramics doped with Sb, Ag and Te, Journal of materials Science Letters, 413, 1994, 1654.

14. C.G. Lee, X.D. Wei, J.W. Kysar, J. Hone, Measure-ment of the elastic properties and intrinsic strength of monolayer graphene, Science, 321, 5887, 2008, 385-388.

15. A.A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao, Superior thermal conduc-tivity of single-layer graphene, Nano Lett., 8, 3, 2008, 902-907.

16. M. Orlita, C. Faugeras, P. Plochocka, P. Neugebauer, G. Martinez, D.K. Maude, Approaching the dirac point in highmobility multilayer epitaxial graphene, Phys. Rev. Lett., 101, 26, 2008, 267601.

17. D.R. Dreyer, S. Park, C.W. Bielawski, R.S. Ruoff, The chemistry of graphene oxide, Chem. Soc. Rev., 39, 1, 2010, 228-240.

18. B.H. Nguyen, V.H. Nguye, Promising applications of graphene and graphene-based nanostructures, Ad-vances in Natural Sciences: Nanoscience and Nano-technology, 7, 2, 2016, 023002; doi:10.1088/2043-6262/7/2/023002.

19. V. Dhand, K.Y. Rhee, H.J. Kim, D.H. Jung, A Com-prehensive Review of Graphene Nanocomposites: Research Status and Trends, Journal of Nanomateri-als, 2013, 14.

20. A. Shalaby, L. Aleksandrov, R. Iordanova, A. Stane-va, Y. Dimitriev, Synthesis and characterization of glass doped reduced graphene oxide, J. Chem.


1222

Techn. Metall., 50, 4, 2015, 474-477.21. A. Shalaby, A. Staneva, L. Aleksandrov, R. Iordano-

va, Y. Dimitriev, Phase transformation of RGO/ SiO2 nanocomposites prepared by the sol-gel technique, In: Nanoscience Advances in CBRN Agents Detec-tion, Information and Energy Security, P. Petkov et al. (eds.), NATO Science for Peace and Security Se-ries A: Chemistry and Biology, Springer Link, 2015, 265-272, doi: 10.1007/978-94-017-9697-2_26.

22. A. Shalaby, Sh. Safwat-Mansour, A.S. Afify, M. Hassan, A. Staneva, Synthesis of RGO/SiO2 and Ag/RGO/SiO2 Nanocomposites and Study of Their Sensitivity towards Humidity, In: Nanoscience Advances in CBRN Agents Detection, Information and Energy Security, P. Petkov et al. (eds.), NATO Science for Peace and Security Series A: Chemistry and Biology, SpringerLink, 39, 2018, 397-405.

23. M. Colie, D. Mihaiescu, A. Surdu, R. Trusca, B. Va-sile, D. Istrati, A. Ficai, C. Plapcianu, E. Andronescu, High temperature superconducting materials based on Graphene/YBCO nanocomposite, 6th Interna-tional conference on Advanced Nano Materials, Materials Today: Proceedings 3, 2016, 2628-2634.

24. S. Dadras, S. Dehghani, M. Davoudiniya, S. Falahati,

Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping, Materials Chemistry and Physics, 193, 2017, 496-500.

25. B. Sahooa, K.L. Routraya, D. Samalb, Dhruba-nanda Beheraa, Effect of artificial pinning centers on YBCO high temperature superconductor through substitution of graphene nano-platelets, Materials Chemistry and Physics, 223, 2019, 784-788.

26. Yang, Songlin, Zhang, Jin, Deposition of YBCO nanoparticles on graphene nanosheets by using matrix-assisted pulsed laser evaporation, Optics and Laser Technology, 109, 2019, 465-469.

26. Shih-Jye Sun, Hsiung Chou, Triplet superconduct-ing p+ip pairs existing in a graphene sandwiched by superconductor and ferromagnet, Physics Letters A, 382, 2018, 3012-3017.

28. S. Dadras, S. Falahati, S. Dehghani, Effects of graphene oxide doping on the structural and superconducting properties of YBa2Cu3O7−δ, Volume 548, 2018, 65-67.

29. D. Kichukova, A. Staneva, D. Kovacheva, I. Tzoneva, Exploring the impact of different soft reducers in re-duced graphene oxide synthesis, Journal of Chemical Technology and Metallurgy, 54, 4, 2019, 845-854.

synthesis and characterization of ybco and …janna mateeva, anna staneva, boris martinov, blagoy...

Documents