K.A. Shaihutdinov

Composite materials on high-Tc superconductors and BaPbO3, Ag basis

The preparation, processing and characterization of the composite materials on high-T c superconductor (HTSC) basis, YBa 2 Cu 3 O 7 /Ag and Y 0.75 Lu 0.25 Ba 2 Cu 3 O 7 /BaPbO 3 , is reported. The initial components YBa 2 Cu 3 O 7 and BaPbO 3 were prepared by the standard solid state reaction technique. The microstructures of the samples were observed by scanning electron microscopy, whilst the XRD paterns of the composites HTSC+Ag and HTSC+BaPbO 3 revealed the 123 superconducting phase and the Ag or BaPbO 3 structure. The chemical compositions of the powders and the interface zone were found by employing energy dispersive spectrometry. The resistive and magnetic measurements of the composites indicated the transition temperature 93.5 K. Application of such composite materials in the construction of a superconducting fault current limiter model is reported.

Synthesis, microstructure, and the transport and magnetic properties of Bi-containing high-temperature superconductors with a porous structure

Preliminary data on the synthesis and physical properties of polycrystalline Bi1.8Pb0.3 Sr2Ca2Cu3Ox high-temperature superconductors of low density with a foam-like microstructure are reported.

A comparative study of transport properties of composites HTSC + MgTiO3 and HTSC + NiTiO3. The effect of paramagnetic NiTiO3

Abstract Bulk composites Y3/4Lu1/4Ba2Cu3O7+NiTiO3 and Y3/4Lu1/4Ba2Cu3O7+MgTiO3 with insulator volume content 7.5% and 15% modelling a network of Superconductor-Insulator-Superconductor (S-I-S) junctions have been prepared. The ρ(T) dependences of composites HTSC+MgTiO3 are described well by the mechanism of Thermally Activated Phase Slippage (TAPS). The anomalous behavior of resistivity ρ(T) of HTSC+NiTiO3 composites manifesting as a kink on ρ(T) curves at some temperature Tm have been observed. In the temperature range Tm

Highly Textured Bismuth-Containing High-Temperature Superconductor Ceramics Obtained by Uniaxial Pressing in Liquid Medium: Fabrication and Properties

A new method of fabricating textured ceramics with a composition of Bi1.8Pb0.3Sr1.9Ca2Cu3Ox is described, according to which the initial low-density ceramics is subjected to uniaxial pressing in a liquid medium followed by drying and annealing. Analysis of the X-ray diffraction and scanning electron microscopy data show evidence for a high degree of texture in high-temperature superconductor ceramics fabricated using the proposed method. The results of magnetic measurements indicate that the obtained material possesses anisotropy of the magnetic moment for the magnetic field H oriented parallel and perpendicular to the direction of uniaxial pressing. The textured ceramics also show high diamagnetic response for H parallel to the c axis of grains, which makes these ceramics promising materials for practical applications.

The anomalous transport properties of composites HTSC+NiTiO3

Abstract Bulk composites Y 3/4 Lu 1/4 Ba 2 Cu 3 O 7 +NiTiO 3 and Y 3/4 Lu 1/4 Ba 2 Cu 3 O 7 +MgTiO 3 with insulator volume content 7.5% and 15% modeling a network of superconductor–insulator–superconductor junctions have been prepared. The temperature dependences of resistivity ρ ( T ), critical density J c ( T ) and current–voltage characteristics (CVCs) are presented. The anomalous behavior of ρ ( T ) of Y 3/4 Lu 1/4 Ba 2 Cu 3 O 7 +NiTiO 3 composites manifesting as a kink on ρ ( T ) curves at some temperature T m has been observed. In the temperature range T m T T c the dissipation is Ohmic while below T m the CVCs are strongly non-linear. This peculiarity is interpreted as arisen owing to Abrikosov vortices flow. The ρ ( T ) dependences of composites Y 3/4 Lu 1/4 Ba 2 Cu 3 O 7 +MgTiO 3 are fitted well by the mechanism of thermally activated phase slippage using assumption of potential barrier of different length. There is a knee on the J c ( T ) of composite sample Y 3/4 Lu 1/4 Ba 2 Cu 3 O 7 +NiTiO 3 correlating with Neel temperature of antiferromagnetic NiTiO 3 .

Thermally activated phase slippage in composites HTSC + CuO

Abstract The effect of thermally activated phase slippage (TAPS) in composites HTSC + CuO has been studied. The experimental ϱ(T) dependences have been treated within framework of TAPS using temperature dependences of critical current for tunnel S-I-S junctions.

Controlled magnetoresistance in Y3/4Lu1/4Ba2Cu3O7-CuO composites at 77 K

We have studied the low-temperature magnetoresistance of Y3/4Lu1/4Ba2Cu3O7-CuO composites obtained by fast sintering technique and established a relation between the probing to critical current density ratio j/jc and the shape of the magnetoresistance curve ρ(H). For j/jc<1, the electric resistance arises at a threshold value of the magnetic field strength Hc. For j/jc≥1, a linear variation of ρ(H) at 77 K in the range from 0 to 14 Oe can be provided by selecting the CuO content (in the 15–30 vol % interval) and the j value (in the 0.003–0.2 A/cm2 range). In the latter case, the slope dρ/dH (i.e., the sensitivity of the electric resistivity with respect to the magnetic field) is 1–20 mΩ cm/Oe and the relative field-induced increase in the resistivity ρ0=(ρ(H)−ρ(H=0))/ρ(H=0) amounts to 1320 and 685% at H=200 and 35 Oe, respectively. Composites possessing controlled magnetoresistance are promising materials for the active elements of magnetic field sensors capable of operating at a practically convenient liquid nitrogen temperature.

Transport properties of composites high temperature superconductor + semiconductor with different carrier concentration

Abstract Composites HTSC + semiconductor with different carrier concentrations were prepared as a model of Josephson type contacts. Experimental temperature dependences of the critical current density Jc(T) in the composites are presented. The best congruence of experiment with theory was reached for the Schussler-Kummel consideration of Andreev scattering in S-Sm-S (S-superconductor, Sm-semiconductor) junctions.