999 ISSN 2075-1133, Inorganic Materials: Applied Research, 2019, Vol. 10, No. 4, pp. 999–1002. © Pleiades Publishing, Ltd., 2019. Russian Text © The Author(s), 2019, published in Materialovedenie, 2019, No. 2, pp. 34–37. The Influence of CuO Dopant Nanoparticles, Prepared via the Arc Plasma Synthesis Method, on the Critical Current of YBa 2 Cu 3 O 7 – δ Composites A. V. Ushakov a, b, *, I. V. Karpov a, b , A. A. Lepeshev a, b , M. I. Petrov c , L. Yu. Fedorov b , D. M. Gokhfel’d c , S. M. Zharkov b, c , G. M. Zeer b , V. G. Demin b , and A. K. Abkaryan b a Federal Research Center Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia b Siberian Federal University, Krasnoyarsk, 660041 Russia c Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia *е-mail: sfu-unesco@mail.ru Received January 11, 2018; revised April 17, 2018; accepted July 31, 2018 Abstract—YBa 2 Cu 3 O 7 – δ –CuO composites with CuO particle contents of 0.5, 1.0, 2.0, 5.0, 10, 15, 20, and 24% were produced via arc plasma synthesis. Their magnetic properties were analyzed in the context of the expanded critical state model. In comparison with a reference sample, the critical current intragranular den- sity increased in composites with CuO concentrations of 0.5, 1, 20, and 24%. The mechanisms of the influ- ence of nanodopants on the change in the critical current density at various volume contents of nano-CuO were proposed as well. Keywords: nanodispersed powder, high-temperature superconductor, copper oxide, vacuum arc DOI: 10.1134/S2075113319040439 INTRODUCTION The critical current density J c is an important char- acteristic of a superconducting material in practical applications. This quantity describes the maximum electric current passing through a superconductor with no energy dissipation at the given temperature and magnetic field. In type-II superconductors (all high-temperature superconductors (HTSC)), the energy dissipation occurs owing to the Abrikosov vor- tices on account of their interaction with a transport current or the screening currents in a superconductor. The movement of vortices may be substantially reduced via the creation of Abrikosov vortex pinning centers. Since the Abrikosov vortex diameter is com- parable with the double coherence length, the prefer- able pinning center size for HTSCs is several tens of nanometers. The problem of the creation of pinning centers in HTSCs, as well as their thermal and chemi- cal stability, is thoroughly described in the literature [1–5]. The study of transport properties of HTSC + CuO composites simulating the network of weak S–I–S bonds revealed that the chemical interaction of YBa 2 Cu 3 O 7 with CuO is negligibly weak [6]. The development of the arc plasma method for the synthe- sis of CuO nanoscales aroused interest in the investi- gation of the effect of CuO nanoinclusions on the transport properties of superconducting YBa 2 Cu 3 O 7 polycrystals. EXPERIMENTAL Artificial pinning centers were created by using CuO nanodispersed powders with a characteristic granule size below 10 nm. The CuO nanopowder was synthesized in a plasma chemical reactor in accor- dance with a technique described in [7, 8]. The arc evaporator used in the synthesis exhibited the follow- ing characteristics: the pulse arc discharge current was 2.3 kA and the strength of the longitudinal magnetic field on the cathode surface, generated by the coil, was 80 mT. The sputtering cathode was technically pure copper. In order to activate the plasma chemical reac- tions, the chamber was purged with a 10% О 2 + 90% Ar gas mixture after the pre-evacuation to a pressure of 1 mPa. The synthesis was conducted at a pressure of 10 Pa. Before the evaporation, the cathode was heated to 700 K. The copper oxide nanopowder had a black color. The weight concentrations of dopants were 0– 24 wt %. YBa 2 Cu 3 O 7– δ specimens with various CuO nanoparticle contents were produced in accordance with a conventional ceramic technology. A mixture of YBa 2 Cu 3 O 7– x powders and CuO nanoparticles was