Structural and electrical studies of mixed copper/ruthenium oxides and related compounds of zinc and antimony

doi:10.1016/S0022-4596(05)80268-3

Journal of Solid State Chemistry

Volume 96, Issue 2, February 1992, Pages 344-359

https://doi.org/10.1016/S0022-4596(05)80268-3 Get rights and content

The preparation and characterization of a number of mixed metal oxides of ruthenium and copper are described, the compounds being chosen to demonstrate the changes that occur on moving from the 3-D perovskite structure to the 2-D K₂NiF₄ structure via the intermediate Ruddlesden-Popper structure. Full structure refinements by neutron powder diffraction are reported for SrLaCuRuO₆, SrLaCuSbO₆, Sr₃NdCuRuO₈, Sr₃LaCuRuO₈, Sr_3.5La_0.5CuRuO_8−δ, Sr₃LaZnRuO₈, Sr₂LaCuRuO_7−δ, and Sr_2.15La_0.85 CuRuO_7−δ. There is no evidence for the presence of Cu³⁺ in any of these samples. The electrical conductivities of these phases, and also those of Sr_1.2La_0.8CuRuO_6−δ and Sr₂LaZnRuO₇, have been measured as a function of temperature. All these materials are semiconductors, but none shows long range magnetic order at 1.5 K.

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Composition driven structural transition in La<inf>2−x</inf>Sr<inf>x</inf>CuRuO<inf>6</inf>(0 ≤ x ≤ 1) double perovskites
2017, Journal of Alloys and Compounds
Citation Excerpt :
But, later x-ray diffraction experiments using synchrotron radiation have established that monoclinic spacegroup P21/n is better suited than the orthorhombic spacegroup Pbnm to describe the structure of this composition [8]. It is to be noted that Sr doping at La site beyond half doping apparently leads to oxygen deficient samples as Cu remains in the +2 oxidation state in the sample Sr1.2La0.8CuRuO6−δ [7]. The fact that the doped holes reside at Ru site is also proved by x-ray photo emission studies on a series of these compounds, La2−xSrxCuRuO6 [9].
We report results of detailed structural investigations on the system La_2−xSr_xCuRuO₆ (0 ≤ x ≤ 1) as a function of composition using neutron powder diffraction. Our results reveal that this series of compounds exhibit an interesting structural transition manifested through Sr doping; with Ru in single valency, in end members, and mixed valency otherwise. The end members La₂CuRuO₆ and LaSrCuRuO₆ crystallize in monoclinic structures with space group P2₁/n. However, the compositions with intermediate Sr doping (x = 0.2 and 0.8) crystallize in triclinic structure with space group P-1, albeit with minute distortions. The detailed structural studies by neutron powder diffraction at room temperature and at 10 K, for compositions, x = 0.2, 0.8 and 1 are presented. While magnetic measurements are indicative of ferro and antiferromagnetic like transitions for x = 0 and x > 0 respectively, neutron diffraction patterns collected at 10 K and 30 K across the characteristic transition temperature suggested by the magnetic data, do not show any extra peaks or extra intensity at lower temperature as compared to the high temperature, thus, establishing the absence of any long-range magnetic ordering in these samples.
Crystal structure, oxidation state and magnetism of Sr<inf>x</inf>La <inf>2-x</inf>Cu<inf>0.5</inf>Ru<inf>0.5</inf>O<inf>4</inf> (x=1, 1.5)
2014, Journal of Solid State Chemistry
Citation Excerpt :
Confirming the conclusions drawn from the Ru 3d XPS spectra, the recorded Ru 3p core level spectra (Fig. 6) show that the Ru 3p3/2 peak appears nearly 0.5 eV higher in Sr1.5La0.5Cu0.5Ru0.5O4 than in SrLaCu0.5Ru0.5O4. Since according to Cu XPS data of the latter oxide, this element is only present in the 2+ oxidation state these results reveal that charge compensation due to La replacement by Sr is achieved in Sr1.5La0.5Cu0.5Ru0.5O4 by the oxidation of Ru4+ rather than by the Cu2+ oxidation in agreement with previous reports [3,13]. In SrLaCu0.5Ru0.5O4 the detailed analysis of Cu and Ru XPS data lead to the conclusion that Ru exists as Ru4+ and Ru5+ (Ru4+ predominant) and Cu as Cu2+ and Cu+ (Cu2+ predominant).
Sr_xLa_2−xCu_0.5Ru_0.5O₄ (x=1, 1.5) oxides with K₂NiF₄-type structure were prepared by solid state reaction and characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, magnetic and electrical resistivity measurements. The SrLaCu_0.5Ru_0.5O₄ phase was obtained for the first time with a negligible amount of impurities. The octahedral Cu/RuO₆ units are more elongated in SrLaCu_0.5Ru_0.5O₄ than in Sr_1.5La_0.5Cu_0.5Ru_0.5O₄ indicating a greater extent of static Jahn–Teller distortion. XPS suggests that mixed ion pairs Ru⁵⁺/Ru⁴⁺↔Cu⁺/Cu²⁺ are present in SrLaCu_0.5Ru_0.5O₄, while Ru remains as Ru⁵⁺ and Cu as Cu²⁺ in Sr_1.5La_0.5Cu_0.5Ru_0.5O₄. Both samples show spin-glass behavior, which can be explained by competition between ferromagnetic and antiferromagnetic superexchange interactions. The negative Weiss temperature estimated for SrLaCu_0.5Ru_0.5O₄, −318 K, is significantly lower than −11.5 K deduced for Sr_1.5La_0.5Cu_0.5Ru_0.5O₄ which may be related to the higher static Jahn–Teller distortion in the former oxide.
Structural characterization of SrLaMnRuO<inf>6</inf> by synchrotron X-ray powder diffraction and X-ray absorption spectroscopy
2008, Solid State Sciences
Citation Excerpt :
Superconductivity and magnetic ordering are reported to coexist in Sr2RuGdCu2O8 [6]. Structural and magnetic properties of these materials are also found to be dependent on cation inversion (BB′ antisite disorder) as well as on doping [7]. More recently, ferromagnetic transitions with high Curie temperature (∼225 K) have been reported in SrLaMnRuO6 [8].
Single-phase polycrystalline powder samples of SrLaMnRuO₆ were prepared by solid-state synthesis method and its crystal structure was studied using synchrotron X-ray diffraction and X-ray absorption spectroscopies. The Rietveld analysis of the room temperature synchrotron X-ray diffraction data shows that it has a double perovskite structure with disordered arrangements of Sr/La and Mn/Ru and adopts orthorhombic space group Pbnm [a = 5.5004(3) Å, b = 5.5445(3) Å, c = 7.7713(5) Å, V = 237.00(3) Å³]. The X-ray absorption near edge spectra (XANES) show that both Mn and Ru occupy octahedral sites in agreement with the synchrotron X-ray diffraction measurements and that the oxidation state of Mn is +3. Extended X-ray absorption fine structure (EXAFS) analyses of Mn K edge spectra showed that the local order around Mn/Ru can be described as distorted Mn/RuO₆ octahedra with three different Mn/Ru–O bond lengths. The local structure as determined from EXAFS is in good agreement with the average structure determined from synchrotron X-ray diffraction measurements.
Synthesis, structure, magnetic properties and structural distortion under high pressure of a new osmate, Sr<inf>2</inf>CuOsO<inf>6</inf>
2008, Journal of Solid State Chemistry
A new osmate Sr₂CuOsO₆ was synthesized and its structure refined using powder synchrotron X-ray diffraction. The results of the Reitveld refinements indicate complete B-cation order in a double perovskite crystal structure. Furthermore, the analysis of the B-cation bond lengths indicates a symmetric coordination around Os, as opposed to a significant distortion of Cu–O bond lengths. The octahedral distortion around Cu(II) is characteristic of a Jahn-Teller distortion. Within the crystal structure of Sr₂CuOsO₆, the long Cu–O bonds are aligned in the same direction along the c-axis in the tetragonal unit cell. This parallel arrangement of long Cu–O bonds produces a lattice parameter ratio, c/(2^1/2a), that is greater than unity. The magnetic susceptibility of Sr₂CuOsO₆ was measured using a SQUID magnetometer and was observed to be consistent with an assignment of Cu(II)–Os(VI) formal oxidation states, thus confirming the bond valences calculated on the basis of the crystal structure. In perovskites, octahedral tilting and bond shortening are two competing compression mechanisms. Compression mechanisms of this double perovskite were characterized using high-pressure synchrotron X-ray diffraction. Application of hydrostatic pressure up to 6 GPa significantly decreased the lattice parameter ratio, demonstrating the primary compression mechanism is a shortening of the long Cu–O bond.
The crystal structure of CaLaMnFeO<inf>6</inf> double perovskite
2005, Materials Letters
Citation Excerpt :
The Rietica programme [15,25] was used for the structural refinements of neutron diffraction data. Three general classes of double perovskite are listed on the basis of B-cation arrangement, namely (1) the distorted or random perovskite crystallizing in the Pmm or the orthorhombic space group Pbnm[16,17]; (2) the rock salt type with a space group Fmm space group, which also has a monoclinic variation P21/n[16,18]; and (3) the layered type crystallizing in P21/m[19]. Owing to the lack of crystal structure information, Structure Prediction and Diagnostic Software (SPuDS) [20] was employed to get the initial structural data.
A single-phase, polycrystalline sample of the double perovskite CaLaMnFeO₆ was prepared by solid-state synthesis and characterized with neutron powder diffraction. The compound belongs to the class of AA′BB′O₆ perovskites with a random distribution of Mn and Fe atoms over the B-cation sub-lattice. Rietveld refinement of the room temperature neutron powder diffraction data revealed that the crystal structure of CaLaMnFeO₆ is disordered with orthorhombic symmetry (space group Pbnm) having lattice parameters a = 5.4468(5) Å, b = 5.4386(5) Å, c = 7.6862(5) Å. The crystal structure is distorted due to the small size of the La⁺³ and Ca⁺² cations, which force the (Mn/Fe)O₆ octahedra to tilt in order to optimize the 12-coordinated (La/Ca)–O bond distances.
Structural chemistry of the cation-ordered perovskites Sr <inf>2</inf>CaMo<inf>1-x</inf>Te<inf>x</inf>O<inf>6</inf> (0≤x≤1)
2005, Journal of Solid State Chemistry
The crystal structures of Sr₂CaMoO₆ and Sr₂CaTeO₆ have been determined at room temperature by neutron powder diffraction. Both compounds crystallize in the perovskite structure with a rock-salt ordered array of Ca²⁺ and M⁶⁺ cations (M=Mo, Te) on the six-coordinate sites (space group P2₁/n (no. 14); for M=Mo, $a = 5.76228 (7)$ , $b = 5.84790 (7)$ , $c = 8.18707 (9) Å$ , $β = 90.194 (1) °$ , for M=Te, $a = 5.79919 (9)$ , $b = 5.83756 (8)$ , $c = 8.2175 (1) Å$ , $β = 90.194 (1) °$ ). Compositions in the solid solution Sr₂CaMo₁₋_xTe_xO₆ have been synthesized and shown by X-ray diffraction to adopt the same ordered structure. The results are used in a discussion of the cation oxidation states in Ca₂FeMoO₆ and to establish the similarity between the structural chemistry of hexavalent Mo and Te.

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Regular articleStructural and electrical studies of mixed copper/ruthenium oxides and related compounds of zinc and antimony

J. Solid State Chem.

Mater. Res. Bull.

J. Inorg. Nucl. Chem.

J. Solid State Chem.

J. Solid State Chem.

J. Solid State Chem.

J. Solid State Chem.

Regular article
Structural and electrical studies of mixed copper/ruthenium oxides and related compounds of zinc and antimony