Effects of TiO2 nanoparticle addition on the flux pinning properties of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ ceramics

The effects of adding TiO2 nanoparticles on the flux pinning properties of the Bi-Pb-Sr-Ca-Cu-O (BPSCCO) system were investigated. Polycrystalline samples of (Bi1.6Pb0.4Sr2Ca2Cu3O10+delta)1-x(TiO2)x, where x = 0.000, 0.002, 0.004, 0.006, 0.008, and 0.010, were fabricated by the conventional solid-state reaction method. The Xray diffraction (XRD) results showed that all samples consisted of Bi-2223 and Bi-2212 phases. The Bi-2223 volume fraction decreased with the addition of TiO2. Scanning electron microscopy (SEM) examination presented a degradation in texture structure with increasing misoriented grain and porosity with high doping contents. The critical temperature was decreased by TiO2 appearance in relation to Bi-2223 deceleration. Critical current density dependence on the magnetic field Jc(B) was enhanced with x = 0.002, 0.004 and reached maximal values on the x = 0.002 sample. In the collective pinning theory framework, the small bundle field (Bsb) and the large bundle field (Blb) were estimated, revealing the extension of the small and large bundle regimes with proper amounts of dopant. The temperature-dependent normalized critical current density (j) indicated that delta l pinning is the dominant flux pinning mechanism in all samples. The Dew-Hughes model analyzed the pinning center properties and confirmed that TiO2 nanoparticles create normal core point pinning centers in the matrix.