Composition analysis of Ca-doped YBa₂Cu₃O_7−δ/Y₂BaCuO₅prepared by the top-seeding melt-texture growth

Abstract

The Ca-doped YBa2Cu3O7−δ/Y2BaCuO5 bulk-textured superconductors were prepared by using the top-seeding melt-textured growth process. Composition analyses were made for such prepared samples. We found that Ca concentration in the YBa2Cu3O7−δ grains decreased along the growing direction; Ca preferred to substitute Y in the YBa2Cu3O7−δ grains, rather than to stay at the grain boundary. The accumulation of extra CuO at the growth front was considered as one of the causes of the inhomogeneous distribution of Ca.

Effect of Ca doping on microstructural and superconducting properties of DyBa2Cu3O7 /Caz(0 z 0.2) ceramics

“…It seems that such concentration is close to the limit of Ca solubility in the '211' phase for the sintered 123/Ca z ceramics, because in both compositions 123/0.1 Ca and 123/0.2 Ca it was practically the same. According to the data from the literature [20] in the melt-textured YBa 2 Cu 3 O 7−δ /Y 2 BaCuO 5 ceramics doped by Ca, Ca concentration varied from 1.9 to 2.6 at%. This discrepancy with our data can be explained by the difference between the ceramic processing in both cases.…”

“…According to [22], in sintered ceramics no more than 50% 'clean' GBs can be considered to have a favourable geometry for supercurrent and the percolation threshold is equal to 12% [23]. We made a systematic statistical study of grain boundaries similar to that performed earlier for YBaCuO ceramics doped with Ag [20] and DyBaCuO doped with Pt [21] and ZrO 2 [19]. So, about 50 consecutive boundaries in the sample were characterized by bright-field tilting imaging in a TEM under a tilt spread ranging from −25 • to +25 • .…”

Crystal growth orientation and microstructure of Y0.9Ca0.1Ba2Cu3O7− melt grown bars

“…Other works present investigations of calcium doping for Y123 bulk material [2,3]. In this case, the basic idea is always to improve the inter-grains J c by reducing the weak link behavior of GBs.…”

“…Moreover, this work reports an inter-grains J c enhancement which is attributed to the calcium doping. In term of growth mechanisms, He [3] shows that, in the case of Ca-doped Y123 (namely (Y,Ca)123 for brevity) grains grown from the melt, Ca would enter the Y123 grains rather than the created GBs. This observation is not contradictory with Berenov's conclusion [2] since, in that case, no growth phenomenon from the melt occurs.…”