Investigation of intra- and intergranular coupling of ferroelectric-superconducting composites

Abstract

We investigated the coupling of specific ferroelectric-superconducting composites with variable volume fraction, particularly because they have presented a superconducting transition at 85 K. The intra- and intergranular coupling of these composites has been considered from the resistivity and susceptibility measurements. Our results show that the transport properties of this kind of composite are governed by different mechanisms, depending on the volume fraction of the ferroelectric material, . Up to intragranular coupling exists between the YBCO superconducting grains, but when the electrical transport is greatly related to intergranular coupling. In this case, two distinct and superconducting phases are evidenced by the susceptibility measurements; they maintain the superconducting character of the composites. Moreover, at the superconducting percolation threshold, the electrical response exhibits some hysteresis giving evidence that internal polarization is important and can play a role in the composite properties.

Magnetic Properties of YBCO-PST Composites

“…"Green phase" usually appears during sintering of the pure YBCO and was actually found in the X-ray spectra of the composites [6,10]. The EPR spectrum of YBCO-PST sample Φw = 0.75 is similar to the previous one.…”

The effect of paramagnetic impurities in normal metal on the critical current in a network of S N S Josephson junctions in bulk Y3/4Lu1/4Ba2Cu3O7 BaPb1 xFexO3composites

“…On the other hand, HTSC-based composites are a typical example of a weak-link network with a non-superconducting component playing the role of barriers separating the HTSC crystallites [21][22][23][24][25][26][27][28][29][30][31]. Although the transport properties of such composites are affected by the distribution function of the geometrical parameters of the nonsuperconducting layers [32], nevertheless, the main features of the resistive state of the composites remain the same as those of some single weak links [24,26,28,31].…”

Superconductor-semiconductor-super- conductor junction network in bulk polycrystalline composites Y3/4Lu1/4Ba2Cu3O7+ Cu1-xLixO

“…In HTSC-based composites, the nonsuperconducting material (normal metal (N) [3][4][5][6][7][8][9][10][11][12][13][14] or insulator (I) [15][16][17][18][19][20]) plays the role of artificially created grain boundaries. HTSC-based composites are of considerable interest not only because of their possible practical applications, but also as objects for studying intergrain coupling [5, 7-9, 14, 17, 19, 20].…”

“…Analysis of the transport properties of the composites in terms of the various models developed for Josephson junctions should indicate applicability (or inapplicability) of these models to HTSC. Experimental works are presently focused on HTSC + normal metal [3][4][5][6][7][8][9][10][11][12][13][14] or HTSC + insulator [15][16][17][18][19][20] composites. Superconductor-semiconductorsuperconductor (S-Sm-S) junctions are weak links with intermediate properties between that of tunnel and S-N-S junctions.…”

“…Making the baking time shorter leads to a shift and broadening of the superconductornon-superconductor percolation threshold to lower nonsuperconductor content in contrast to composites prepared by prolonged heat treatment. In the case of fast baking, the transport current flows through both superconductor and non-superconductor grains at relatively small concentrations (7-45 vol%) of the latter ingredient [19,20]. Therefore, the effective thickness of layers between superconductor crystallites can be easy changed by varying the relative volume content of components of a composite [13,20].…”