Material for resistive barriers in Bi-2223/Ag tapes

Abstract

The reactivities of several oxide materials (OM) in direct contact with BSCCO powder has been tested at a temperature of approximately 845 • C in air. The OM such as BaZrO 3 , SrCO 3 , MgO and ZrO 2 showing little or no reactivity with BSCCO were mixed (10 wt%) with a BSCCO precursor powder and used for monocore tapes made by a standard powder-in-tube technique. The microstructure of the BSCCO+OM cores was analysed by SEM and XRD and the transport current properties-critical current, pinning force and resistance up to 16 T-were measured as a function of the magnetic field for various orientations with respect to the ab plane. The OM used influenced the electrical properties of the Bi-2223 phase in different ways. This is because the oxides react with BSCCO during the heat treatment and simultaneously affect the 2212 → 2223 phase transformation as well as the Bi-2223 grain growth and grain connectivity. Submicrometre commercial SrCO 3 powder was evaluated as the best material from all those tested, for resistive barriers in Bi-2223/Ag tapes.

Preparation and enhancement of critical current density in MgB2wires and tapes

“…J c is further improved to 1.7 × 10 4 A cm −2 in 1 T at 29.5 and 33 K in self-field [17]. Also, transport J c of 8700 and 55 830 A cm −2 at 4.2 K in self-field were measured for Cu and Fe/Cu sheathed MgB 2 square wires by using commercial MgB 2 powder [18]. To date, two important factors of low density and poor flux pinning are the main obstacles to obtaining J c in MgB 2 samples.…”

Magnetic relaxation and lower critical field in MgB2wires

“…J c is further improved to 1.7 × 10 4 A cm −2 in 1 T at 29.5 K and at 33 K in a self-field [10]. Also, transport J c of 8700 and 55 830 A cm −2 at 4.2 K in a self-field were measured for Cu-and Fe/Cu-sheathed MgB 2 square wires, respectively, by using commercial MgB 2 powder [11]. On the other hand, another important feature that should be considered is the magnetic relaxation behaviour of MgB 2 superconductors.…”

The effect of Fe-magnetization onIc(B) andIc( ) characteristics of iron-sheathed MgB2composite wires

“…An Fe tube of 6.0/4.2 mm (outer/inner diameter) was filled with MgB 2 precursor powder, densified and deformed initially by rotary swaging. Then, two-axial rolling [11] was applied to deform the composite into a rectangular wire of 1.17 mm × 1.17 mm (MgB 2 /metal sheath ratio was 47% and 25% for single-and four-core, respectively). No sintering treatment was applied to these composites to keep the transport currents in low level and to allow their transport measurements also in low magnetic fields.…”

“…This was done to speed up the calculations. The shape of I c (B) was calculated by taking into account the real geometry of the iron-sheathed MgB 2 core and the I c (B) dependence measured for a non-magnetic copper-sheathed MgB 2 conductor [11].…”