The role of different negatively charged layers in Ca10(Fe1-xPtxAs)10(Pt3+yAs8) and superconductivity at 30 K in electron-doped (Ca0.8La0.2)10(FeAs)10(Pt3As8)

The recently discovered compounds Ca10(Fe1-xPtxAs)10(Pt3+yAs8) exhibit superconductivity up to 38 K, and contain iron arsenide (FeAs) and platinum arsenide (Pt3+yAs8) layers separated by layers of Ca atoms. We show that high Tc's above 15 K only emerge if the iron-arsenide layers are at most free of platinum-substitution (x \rightarrow 0) in contrast to recent reports. In fact Pt-substitution is detrimental to higher Tc, which increases up to 38 K only by charge doping of pure FeAs layers. We point out, that two different negatively charged layers [(FeAs)10]n- and (Pt3+yAs8)m- compete for the electrons provided by the Ca2+ ions, which is unique in the field of iron-based superconductors. In the parent compound Ca10(FeAs)10(Pt3As8), no excess charge dopes the FeAs-layer, and superconductivity has to be induced by Pt-substitution, albeit below 15 K. In contrast, the additional Pt-atom in the Pt4As8layer shifts the charge balance between the layers equivalent to charge doping by 0.2 electrons per FeAs. Only in this case Tc raises to 38 K, but decreases again if additionally platinum is substituted for iron. This charge doping scenario is supported by our discovery of superconductivity at 30 K in the electron-doped La-1038 compound (Ca0.8La0.2)10(FeAs)10(Pt3As8) without significant Pt-substitution.Comment: 4 pages, 4 figure

Suppression of superconductivity by V-doping and possible magnetic order in Sr2VO3FeAs

Superconductivity at 33 K in Sr2VO3FeAs is completely suppressed by small amounts of V-doping in Sr2VO3[Fe0.93(+/-0.01)V0.07(+/-0.01)]As. The crystal structures and exact stoichiometries are determined by combined neutron- and x-ray powder diffraction. Sr2VO3FeAs is shown to be very sensitive to Fe/V mixing, which interferes with or even suppresses superconductivity. This inhomogeneity may be intrinsic and explains scattered reports regarding Tc and reduced superconducting phase fractions in Sr2VO3FeAs. Neutron diffraction data collected at 4 K indicates incommensurate mag- netic ordering of the V-sublattice with a propagation vector q = (0,0,0.306). This suggests strongly correlated vanadium, which does not contribute significantly to the Fermi surface of Sr2VO3FeAs.Comment: text revised, magnetic q-vector added, one reference added 4 pages, 4 figure

SnCN₂: A Carbodiimide with an Innovative Approach for Energy Storage Systems and Phosphors in Modern LED Technology

The carbodiimide SnCN$_{2}$ was prepared at low temperatures (400 °C–550 °C) by using a patented urea precursor route. The crystal structure of SnCN$_{2}$ was determined from single‐crystal data in space group C2/c (no. 15) with a=9.1547(5), b=5.0209(3), c=6.0903(3) Å, β=117.672(3), V=247.92 Å$^{3}$ and Z=4. As carbodiimide compounds display remarkably high thermal and chemical resistivity, SnCN$_{2}$ has been doped with Eu and Tb to test it for its application in future phosphor‐converted LEDs. This doping of SnCN$_{2}$ proved that a color tuning of the carbodiimide host with different activator ions and the combination of the latter ones is possible. Additionally, as the search for novel high‐performing electrode materials is essential for current battery technologies, this carbodiimide has been investigated concerning its use in lithium‐ion batteries. To further elucidate its application possibilities in materials science, several characterization steps and physical measurements (XRD, in situ XANES, Sn Mössbauer spectroscopy, thermal expansion, IR spectroscopy, Mott‐Schottky analysis) were carried out. The electronic structure of the n‐type semiconductor SnCN$_{2}$ has been probed using X‐ray absorption spectroscopy and density functional theory (DFT) computations

Coordination Polymers with a Pyrazine-2,5-diyldimethanol Linker: Supramolecular Networks through Hydrogen and Halogen Bonds

In this paper, the synthesis and crystal structure of pyrazine-2,5-diyldimethanol (pyzdmH2, C6H8N2O2), a new symmetric water-soluble N,O-chelating tetra-dentate organic ligand, is reported and an environmentally friendly method is used to synthesize coordination compounds in water under ambient conditions, from the reaction of pyzdmH2 with the halide salts of Cu(II), Zn(II), Hg(II) and Cd(II): {[Cu(pyzdmH2)0.5(µ-Br)(Br)(H2O)]·H2O}n 1, {[Zn2(pyzdmH2)(µ-Cl)(Cl)3(H2O)]·H2O}n 2, [Hg2(pyzdmH2)0.5(µ-Cl)2(Cl)2]n 3, {[Cd2(pyzdmH2)(µ-Cl)4]·H2O}n 4, and {[Cd2(pyzdmH2)(µ-Br)4]·H2O}n 5. Single-crystal X-ray diffraction analysis reveals that 1–3 are 1D coordination polymers and 4 and 5 are 3D coordination networks, all constructed by bridging pyrazine-2,5-diyldimethanol and halogen ions. The hydroxyl groups in the organic linker extend the 1D chains to non-covalent 3D networks. In all non-covalent and covalent 3D networks, water molecules are trapped by strong hydrogen bond interactions. Supramolecular analysis reveals strong O-H···O, O-H···N, O-H···X, and weak C-H···O, C-H···X (X = Cl, Br) hydrogen bonds, as well as π-π(pyrazine ring), metal-halogen···π(pyrazine ring), and O-H···ring(5-membered chelate ring) interactions. In addition, X···O weak halogen bonds are present in 1–5 (X = Cl and Br)