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DOE OSTI2020

Materials Data on La(CuO2)2 by Materials Project

La(CuO2)2 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional. La3+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. There are four shorter (2.52 Å) and four longer (2.53 Å) La–O bond lengths. Cu+2.50+ is bonded in a square co-planar geometry to four equivalent O2- atoms. There is two shorter (1.91 Å) and two longer (1.93 Å) Cu–O bond length. O2- is bonded to two equivalent La3+ and two equivalent Cu+2.50+ atoms to form a mixture of distorted edge and corner-sharing OLa2Cu2 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on KLa(CuO2)2 by Materials Project

KLa(CuO2)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to eight equivalent O2- atoms to form distorted edge-sharing KO8 hexagonal bipyramids. All K–O bond lengths are 2.88 Å. La3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All La–O bond lengths are 2.52 Å. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. O2- is bonded to two equivalent K1+, two equivalent La3+, and two equivalent Cu2+ atoms to form a mixture of distorted edge, face, and corner-sharing OK2La2Cu2 octahedra. The corner-sharing octahedra tilt angles range from 0–67°.

36 MATERIALS SCIENCE↗

NASA NTRS1991

Dependence of transition temperature on hole concentration per CuO2 sheet in the Bi-based superconductors

The recently observed variations of the transition temperature (T sub c) with oxygen content in the Bi based (2212) and (2223) superconductors are analyzed in terms of p+, the hole concentration per CuO2 sheet. This analysis shows that in this system, T sub c increases with p+ initially, reaching maxima at p+ = 0.2 approx. 0.3, followed by monotonic decrease of T sub c with p+. The forms of these variations are similar to those observed in the La(2-x)Sr(x)CuO4 and YBa2Cu3Oy systems, suggesting that p+ may be an important variable governing superconductivity in the cuprate superconductors.

Zhao, J.↗

NASA NTRS1987

Superconductivity above 90 K in the square-planar compound system ABa2Cu3O(6 + x) with A = Y, La, Nd, Sm, Eu, Gd, Ho, Er, and Lu

Superconductivity has been found in the 90-K range in ABa2Cu3O(6 + x) with A = La, Nd, Sm, Eu, Gd, Ho, Er, and Lu in addition to Y. The results suggest that the unique square-planar Cu atoms, each surrounded by four or six oxygen atoms, are crucial to the superconductivity of oxides in general. In particular, the high Tc of ABa2Cu3O(6 + x) is attributed mainly to the quasi-two-dimensional assembly of the CuO2-Ba-CuO(2 + x)Ba-CuO2 layers sandwiched between two A layers, with particular emphasis in the CuO(2 + x) layers. Higher-Tc oxides are predicted for compounds with bigger assemblies of CuO2 layers coupled by Ba layers.

Hor, P. H.↗