The Influence of the Polycrystalline State and Partial Dy Substitution on the Superconducting Properties of YBCO

Abstract

The influence of the quasi-equal partial substitution of non-magnetic (Y 3+ )/magnetic (Dy 3+ ) ions in YBa 2 Cu 3 O 7--y on the superconducting properties of the material has been investigated. To minimize the influence of the stress field induced by lattice mismatch, Dy-substituted YBa 2 Cu 3 O 7--y was studied because Y 3+ and Dy 3+ ions have similar ionic radii. The investigation was performed on polycrystalline and powder samples with general formula Dy x Y 1--x Ba 2 Cu 3 O 7--y (x ¼ 0.4-0.6). Higher magnetic losses and intragranular critical current density J c were observed for partially substituted samples in comparison with DyBCO. The strongest influence of magnetic substitution on the electrical resistivity properties was observed in the mixed state.

The Effects of Sb Substitution on Structural Properties in YBa2Cu3O7 Superconductors

“…The first one is the modification of the microstructure in order to obtain fundamental information related to the possible mechanisms, and the second one is to improve its physical characteristics. In order to improve the superconducting properties of Y123, rare earth element doping of the Y site has been investigated [16][17][18][19][20][21][22][23]. It was shown that substitutions at the Y and Ba sites did not generate any discernible effect, while substitution at the Cu and O sites had significant effects on the superconducting properties of cuprates [24].…”

The Effect of Dy Doping on the Magnetic Behavior of YBCO Superconductors

“…It was also reported that the sample Dy 0.6 Y 0.4 Ba 2 Cu 3 O 7−δ has the higher losses and J c at T = 4.2 K in comparison with DyBCO [16].…”

“…We note that Dy substitution increased the critical temperature T c at certain doping rates (when x is 0.2, 0.4, 0.6). Most researchers have found that their Dy-substituted samples show a decrease in T c by using a resistive [4,16] and inductive [11,17] method. The substitution of Dy 3+ ions for Y 3+ ions possibly introduces difference in the electronic state in the CuO 2 plane and affects the transition temperature T c .…”

“…Many researchers have investigated the influence of dopants on Y123 system to improve J c . It was found that Y can be replaced with various rare earth elements [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], including Dy [4,6,11,[15][16][17]19], without any significant change in the critical temperature (T c ) for Re-Ba-Cu-O (123) system (Re = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu). Re elements substitute for both Y and Ba sites in Y123 compounds.…”

“…Some authors [23] are of the opinion that the partial substitution of Y 3+ with a Re ion can lead to changes in the crystal lattice which, in turn, can result in the formation of a stress field causing local flux pinning at the unit-cell level. The presence of a magnetic ion also gives rise to the appearance of a magnetic sublattice, which plays a significant part in the behavior of the partially substituted samples in an external magnetic field [16].…”