Grain boundaries contribution to the complex susceptibility of KCu-Doped YBCO high-temperature superconductors

Nedkov, I.; Veneva, A.

doi:10.1007/bf02397233

Cited by 4 publications

(2 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A second peak, which we associate with intergrain losses, is clearly seen in the case of KCu:YBCO; such a peak was not observed in the case of YBCO (CuO) and Rb:YBCO. Our previous investigations [8] confirmed that the irreversibility line in the (H, T ) plane for the intergranular peak obeyed the h ac = a(1 − t) n law, with different crossovers versus the applied field for YBCO and KCu:YBCO. Figure 3 also shows typical YBCO and KCu:YBCO microstructures, as observed by SEM.…”

Section: Effect Of the Additive Phases On The Grain Boundaries On The...supporting

confidence: 63%

Grain boundary contribution to the a.c. field behaviour of doped YBCO ceramics

Nedkov¹

1998

Supercond. Sci. Technol.

View full text Add to dashboard Cite

The volume of the grain boundaries is a small percentage of the total volume of a polycrystalline superconducting material, but their contribution to the superconductor's properties is paramount. The present work analyses the influence of the variation of the relative fraction of the grain boundary volume, as well as the presence of alkaline additives (K and Rb) and CuO, on the hysteretic losses, the ability to screen low-frequency a.c. fields, the critical current density and the superconducting transition temperature. The data obtained are indicative of a strong dependence on the type of dopant accumulated on the grain boundaries and on the degree of recrystallization of the HTS. The influence of the internal grain pore boundaries caused by the intensification of the recrystallization process is discussed.

show abstract

Section: Effect Of the Additive Phases On The Grain Boundaries On The...supporting

confidence: 63%

Grain boundary contribution to the a.c. field behaviour of doped YBCO ceramics

Nedkov¹

1998

Supercond. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Meanwhile, the value of Tcj decreased from 87.8 K for 0.0 mol% to 85.5 K for 7.0 mol% BZO addition (2.3 K). The decrease of Tcj with the increasing of BZO addition for both COP and SS samples indicates weakening of intergranular coupling perhaps due to the increasing of impurities at the grain boundaries [35,36]. However, the larger decrease of Tcj in the SS samples implies more severe degradation of grain coupling caused by BZO addition compared to the COP samples.…”

Section: X-ray Diffraction (Xrd) Analysismentioning

confidence: 93%

Comparative Study on AC Susceptibility of YBa2Cu3O7−δ Added with BaZrO3 Nanoparticles Prepared via Solid-State and Co-Precipitation Method

et al. 2019

View full text Add to dashboard Cite

Polycrystalline samples of YBa2Cu3O7−δ (Y-123) added with x mol% of BaZrO3 (BZO) nanoparticles (x = 0.0, 2.0, 5.0, and 7.0) were synthesized using co-precipitation (COP) and solid-state (SS) method. X-ray diffraction (XRD) patterns showed the formation of Y-123 and Y-211 as the major and minor phases, respectively. The samples prepared using COP method showed higher weight percentage of Y-123 phase (≤98%) compared to the SS samples (≤93%). A peak corresponding to BZO was also found in the samples added with BZO nanoparticles. The increasing intensity of the BZO peak as the BZO amount increased showed the increasing amount of the unreacted nanoparticles in the samples. Refinement of unit cell lattice parameters indicated that all the samples have an orthorhombic crystal structure and there is no orthorhombic-tetragonal phase transformation. As observed using scanning electron microscopy (SEM), all the samples showed randomly distributed grains with irregular shape. The average grain size for the pure sample prepared using COP method is smaller (0.30 µm) compared with that of the pure SS sample (1.24 µm). Addition of 7.0 mol% BZO led to an increase of average grain size to 0.50 μm and 2.71 μm for the COP and SS samples, respectively, indicating grain growth. AC susceptibility (ACS) measurement showed a decrease in the onset critical temperature, Tc-onset with BZO addition. Comparatively, Tc-onset for the COP samples is higher than that of the SS samples. The value of Josephson’s current, Io increased up to 2.0 mol% BZO addition, above which the Io decreased more drastically for the SS samples. The value of Io is 53.95 μA and 32.08 μA for the 2.0 mol% BZO added SS and COP samples, respectively. The decrease of Io is attributed to the distribution of BZO particles at the grain boundaries as also reflected in the drastic decrease of phase lock-in temperature, Tcj. As a result of smaller average grain size, the presence of more grain boundaries containing insulating BZO particles led to lower Io in the COP samples.

show abstract