Structure of the incommensurate composite crystal [Sr₂Cu₂O₃][CuO₂] _x (x = 1.436)

Abstract

Abstract[Sr2Cu2Oa] [CuO2]x (x = 1.436), Mr=487.5, orthorhombic, ll.tA21ma, ltarA21rna 1,,1 Ts~.J,', Ts~, a = 11.457(5), b = 13.409 (9), c~ = 3.935 (3), c2 = 2.740 (2) A, k~ = b* + 1.436 (2!c~*, k2 = b* + 0.696 (1)c2", V~ = 604.5, I/2 = 420.9A, Z=4, Dx=5.36Mgm-3, MoKa, ,~= 0.71073 A, /x = 28.9 mm-~, F(000) = 890.5, room temperature, final R = 0.057 for 314 unique reflections. The first subsystem [Sr2Cu203] is composed of (Cu203)oo sheets perpendicular to the b axis and Sr ions coordinated to the sheet. The second subsystem is (CuO2)oo infinite chains parallel to the c axis, which are located among the Sr ions of the first subsystem. The atomic positions are modulated along the c axis by the interactions between the two subsystems.

Structural modulation, hole distribution, and hole-ordered structure of the incommensurate composite crystal(Sr2Cu2Gotoh1, Yamaguchi2, Takahashi3 et al. 2003Phys. Rev. B282240View full textAdd to dashboardCite

“…where t is expressed as tϭϪ␥u 3 ϩu 4 . They should be compared with those of the structure model with acentric superspace group, A2 1 ma(01␥)0s0, which was proposed by Ukei et al According to their results,21 the interatomic distances between Sr and O in the CuO 2 range from 1.95 to 2.87 Å, and hence their modulation amplitudes are much larger than those of our results. As we can see from the present comparison, the smaller amplitude of the bondings at the interface between the substructures should be obtained in a more stable and appropriate structure model.…”

“…The lattice constants of orthorhombic average substructures of (Sr 2 Cu 2 O 3 ) 0.70 CuO 2 were refined as a ϭ11.4794(8), bϭ13.4060 (10), and cϭ3.9341(9) Å for the Sr 2 Cu 2 O 3 part and aϭ11.4765 (13), bϭ13.4067 (12), and cϭ2.7519 (19) Å for the CuO 2 one. These values are more accurate than those obtained by Ukei et al, 21 which suggests that the quality of our sample is more appropriate for structure analysis. The composition of (Sr 2 Cu 2 O 3 ) 0.70 CuO 2 was determined from the ratio of cell dimensions of each average substructure.…”

“…Subsequently, Ukei et al have reported the modulated structure analysis of (Sr 2 Cu 2 O 3 ) 0.70 CuO 2 with the use of (3ϩ1)-dimensional superspace-group symmetry. 21 In their modulated structure analysis, the acentric superspace group A2 1 ma(01␥)0s0, for both substructures was employed. According to their results, the distances between Sr in the Sr 2 Cu 2 O 3 substructure and O in the CuO 2 substructure range from 1.95 to 2.87 Å ͓see Fig.…”

Magnetic Ground State of Coupled Edge-SharingCuO2Spin Chains

“…The incommensurate crystal structures consist of planes of quasi 1D CuO 2 chains running along the crystallographic c-axis, stacked alternately with planes of two-leg Cu 2 O 3 ladders. The lattice constants of these subsystems satisfy 10c chain ≈ 7c ladder [11,12]. Materials with different Sr/Ca composition are isostructural with only minor modifications of the bond lengths and angles [13,14,15].…”

Phase diagrams for the YBa2Cu3O7 family — ANNO 1996

“…Only minor variations in the oxygen content are allowed in this arrangement, 1.975<w<2.035, as observed for 0.01 < po2< 100 kPa at 900~ 123]. Srt4Cu24Oah with crystal structure [127,128] described as being incommensurate, {Sr2Cu203; Fmmm, 1145.7(5), 1340.9(9), 393~5(3); +10/7CUO2; Amma; 1145.7(5), 1340.9(9), 274.0(2)} [128] and it is nearly compatible with a 7c=10c' superstructure [124,127]. The oxygen content is almost independent of temperature (Aw < 0.002 per Cu between 670 and 970~ and the relatively high Cu valence vcu=2.24 is preserved until decomposition.…”