The effect of Ag doping on superconducting properties of the Bi-Pb-Sr-Ca-Cu-O tape fabricated by an Ag sheath

An overview of the fabrication and electromagnetic properties of high-temperature conductors processed by the powder-in-tube (PIT) technique with reference to texture development and critical anisotropy data is presented. Special emphasis is given to the optimization of the physicochemical and electromagnetic parameters of the multifilamentary and single-filament conductors with superconducting cores of Bi-2223, Tl-1223 and Y-123 superconducting phases. The influence of the multifilamentary and single-filament structures on texture development is discussed. Also, the importance of the local disturbances of the grain alignment and microdefects for the current distribution across and in the plane of the whole conductor is analysed. A comparative study of the critical current anisotropy with field direction in low magnetic fields of Tl-1223 and Bi-2223 conductors manufactured by the PIT technique is presented. For Tl-1223 PIT conductors the anisotropy coefficient shows a very pronounced minimum, followed by a monotonic reduction of anisotropy with the increase of the magnetic field. This is explained in terms of poor grain alignment with weak intergranular superconducting coupling which cause 3D current percolation and also by the demagnetizing effect of the grains and the ceramic core in the PIT Tl-1223 tapes.

Section: Surface Diffusion Coefficientmentioning

confidence: 69%

Texture development of HTS powder-in-tube conductors

Glowacki

1998

“…In the silver sheathed tapes the Bi-2223 phase forms preferentially at the interface between the silver sheath and the oxide core, because the silver reduces the melting temperature of the oxide. Thus the microstructure near the interface is different from that at the centre of the oxide core [7] and the variations of the tapes thickness and/or width result in different superconducting phase homogeneities.…”

Section: Introductionmentioning

confidence: 99%

Section area and self-field dependence of critical current density in homogeneous bulk textured Bi-2223

Garnier¹,

Desgardin

2001

We report bulk ceramic Bi-2223 transport measurements for samples of various cross sections. The sample preparation process allows the synthesis of large and homogeneous samples. The measurements were carried out at 77 K in self-field (with currents up to 70 A) over a wide range of sample thickness and widths. 17 bars of various sizes, ranging from 0.5 to 3.5 mm width and 0.32 to 3.5 mm thickness, were prepared by sinter forging. The transport critical current density (J CT) clearly decreases as the sample cross section increases, and J −1 CT varies linearly with thickness. This J CT variation cannot be attributed to differences in sample quality (texture, phases, etc) because of the careful synthesis procedure, and implies that the current does not flow uniformly through the samples. The magnetic field dependence of the critical current density (J CM) was compared with the J CT values, allowing us to calculate the induced field, B ind , produced during the J CT measurement. This induced field contributes to a decrease in the measured J CT values. Therefore, the application of a correction factor obtained from B ind on the critical current density results in a value of J C independent of the cross section of the sample. These results question the significance of homogeneous bulk pinning and reveal the possible existence of surface and interface pinning processes.

“…Due to these facts it is reasonable to suppose that silver added to the core would improve the critical current density of Bi2223-Ag tapes, because it would provide an additional 'interface'. The effect of silver additions in Bi2223 tapes has been investigated in several studies [2,[4][5][6][7][8]. The results were somewhat contradictory, but it was generally found that the addition does not significantly improve the properties of the tapes.…”

Section: Introductionmentioning

confidence: 99%

Improved critical current of superconducting Bi2223 - Ag tapes for current lead application by addition of `large' silver particles

Zeimetz

Dou

Liu

1996

The effect of silver additions on the microstructure and superconducting properties of (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O x (Bi2223)-Ag tapes has been investigated. We find a strong dependence on both the silver content and especially the silver particle size. The addition of small (5 µm) particles results in a slight reduction of the critical current. Large (400 µm) particles are squeezed into long flat layers, leading to better grain alignment, grain density and phase purity of the 2223 phase along these layers. As a consequence, the critical current is increased by up to 60% in self-magnetic field, and even more in an external magnetic field.