ORIGINAL PAPER Superconducting properties of nano-sized SiO 2 added YBCO thick film on Ag substrate M A Almessiere*, A l Al-Otaibi and F B Azzouz Department of Physics, College of Sciences, Faculty of Science of Dammam, University of Dammam, Dammam, Saudi Arabia Received: 12 August 2016 / Accepted: 02 February 2017 / Published online: 25 April 2017 Abstract: The microstructure and the flux pinning capability of SiO 2 -added YBa 2 Cu 3 O y thick films on Ag substrates were investigated. A series of YBa 2 Cu 3 O y thick films with small amounts (0–0.5 wt%) of nano-sized SiO 2 particles (12 nm) was prepared. The thicknesses of the prepared thick films was approximately 100 lm. Phase analysis by x-ray diffraction and microstructure examination by scanning electron microscopy were performed and the critical current density dependence on the applied magnetic field J c (H) and electrical resistivity q(T) were investigated. The magnetic field and temperature dependence of the critical current density (J c ) was calculated from magnetization measurements using Bean’s critical state model. The results showed that the addition of a small amount (B0.02 wt%) of SiO 2 was effective in enhancing the critical current densities in the applied magnetic field. The sample with 0.01 wt% of added SiO 2 exhibited a superconducting characteristics under an applied magnetic field for a temperature ranging from 10 to 77 K. Keywords: Y-123 superconductor; Nanoparticles; Critical current; Flux pinning; Magnetic field PACS Nos.: 74.72-h; 74.62.Dh; 74.25.Sv; 74.25.Ha 1. Introduction The high-temperature superconducting (HTS) YBa 2 Cu 3 O 7- d (YBCO or Y-123) ceramic has been considered to be one of the most promising candidates for large-scale applica- tions at liquid-nitrogen temperature under an applied magnetic field. Extensive studies on the bulk ceramics, thick films, and thin films of Y-123 have been performed to optimize their superconducting properties. The effect of granularity/microstructure on the superconducting proper- ties of polycrystalline samples is among one of the greatest challenges in realizing HTS applications. Indeed, the inter- granular critical current density is limited by the weak links between grains boundaries and the intra-granular critical current is impeded principally by the thermally activated flux flow at high temperatures and applied magnetic fields. To prevent the vortex motions and enhance the flux pinning strength, it is necessary to introduce artificial pinning centers in a superconductor, in addition to those that occur naturally. [1–3]. Much attention has been given and various techniques [4–6] have been used to generate artificial pinning centers and improve the performance of superconductors. Based on previous studies, chemical doping and nano- entity additives induce various effects on the microstruc- ture and pinning properties of Y-123. A suitable amount of nano-materials can produce mesoscopic and microscopic defects without affecting the formation of the supercon- ducting phase and the zero-resistance temperature T co . As for the effect of nano-entity additives on the supercon- ducting properties of Y-123, nano-sized insulator inclu- sions have attracted the greatest interest as a class of materials. The addition of Y 2 BaCuO 5 (Y-211) in YEBa 2- Cu 3 O y [7] leads to the formation of an Y 1?x Ba 2-x Cu 3 O y solid solution (low-T c clusters) dispersed in the REBa 2- Cu 3 O y matrix that can act as pinning centers under a high magnetic field. Al 2 O 3 nanoparticles added in YBCO compounds during the final sintering cycle [8] generate nanometric Al-rich inhomogeneities embedded within the superconducting matrix and the sub-grain boundaries are proven to be efficient pinning centers. Perovskite-based nano-additives improve pinning ability by forming com- posites or acting as column defects comprised of self- alighted nanostructures, such as nanodots and nanorods *Corresponding author, E-mail: malmessiere@uod.edu.sa Indian J Phys (October 2017) 91(10):1149–1158 DOI 10.1007/s12648-017-1008-0 Ó 2017 IACS