Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle $YBa_2Cu_3O_{7-δ}$ grain boundaries

Xueyan Song; George Daniels; D. Matt Feldmann; Alex Gurevich; David Larbalestier

doi:10.1038/nmat1394

paper

Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle $Y B a_{2} C u_{3} O_{7 - δ}$ grain boundaries

arXiv:cond-mat/0505568 · doi:10.1038/nmat1394

Abstract

Practical high temperature superconductors must be textured to minimize the reduction of the critical current density $J_{g b}$ at misoriented grain boundaries. Partial substitution of Ca for Y in $Y B a_{2} C u_{3} O_{7 - δ}$ has shown significant improvement in $J_{g b}$ but the mechanisms are still not well understood. Here we report atomic-scale, structural and analytical electron microscopy combined with transport measurements on $7^{\circ}$ $[001]$ -tilt $Y_{0.7} C a_{0.3} B a_{2} C u_{3} O_{7 - δ}$ and $Y B a_{2} C u_{3} O_{7 - δ}$ grain boundaries, where the dislocation cores are well separated. We show that the enhanced carrier density, higher $J_{g b}$ and weaker superconductivity depression at the Ca-doped boundary result from a strong, non-monotonic Ca segregation and structural rearrangements on a scale of ~1 nm near the dislocation cores. We propose a model of the formation of $C a^{2 +}$ solute atmospheres in the strain and electric fields of the grain boundary and show that Ca doping expands the dislocation cores yet enhances $J_{g b}$ by improving the screening and local hole concentration.

19 pages, 6 Figures

Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle $Y B a_{2} C u_{3} O_{7 - δ}$ grain boundaries

Abstract

References in corpus (2)

Cited by in corpus (20)

Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle YBa2​Cu3​O7−δ​ grain boundaries

Abstract

References in corpus (2)

Cited by in corpus (20)

Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low-angle $Y B a_{2} C u_{3} O_{7 - δ}$ grain boundaries