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Cs2Mo2O7 ⋅ CsI is obtained as a member of the series Cs2Mo2O7 ⋅ CsX with X=Cl, Br, and I from the synthesis of Cs2MoO4 with MoO3 and CsX. At room temperature, the compounds crystallize in the space group P63/mmc with the dimolybdate, [Mo2O7]2−, in a linear and eclipsed conformation. Low temperature Raman spectroscopy and low temperature X‐ray diffraction were used to investigate the effect of the ∞2{CsX} ${_\infty ^2 \{ {\rm{CsX}}\} }$ hetero‐honeycomb lattice on the bridging angle of the dimolybdate. For X=Cl, a phase transition occurs below 150 K (P63/mmc → Cmcm). The phase transition relates to a lock‐in that involves bending of the (Mo−O−Mo) bridge. For the Pearson softer iodide compound, no phase transition is observed down to 4 K; thus, the linear configuration remains stable. Specific heat data and their evaluation in terms of phonon contributions are given. [ABSTRACT FROM AUTHOR]

The mixed‐valent, solid solution series FeMo1−nVnO4 (0≤n≤0.3) was synthesized and characterized by x‐ray diffraction, and thermal analysis. Assignments of individual Fe‐species stem from 57Fe‐Mössbauer spectroscopy and DFT‐calculations of the electric field gradients. The incorporation of smaller ions (FeIII, VV) represents an internal "chemical pressure" effect stabilizing the low‐temperature α‐polymorph with increasing n. The site‐preference and distribution of vanadium on individual Mo‐sites impacts the α→β transition temperatures around 650 K, and causes distinct differences in charge mobility in this hole‐doped semiconductor around 225 K. We assign the charge localization in α‐FeMo1−nVnO4 to enhanced electron‐phonon coupling within a polaronic scenario. [ABSTRACT FROM AUTHOR]

Yellow single‐crystals of Na2[Ir(OH)6] were obtained by hydrothermal synthesis in 20 m sodium hydroxide solution at 473 K within 5 hours. X‐ray diffraction on a single‐crystal revealed the trigonal space group R3‾ (no. 148) with lattice parameters a=582.76(3) pm and c=1399.30(8) pm at 100(1) K. Na2[Ir(OH)6] crystallizes in a hettotype of Mg(OH)2 (brucite) and is isostructural to Na2[Sn(OH)6]. The oxygen atoms are arranged in a hexagonal close packing, Na+ and Ir4+ ions occupy the octahedral voids in every second layer in an ordered manner, the voids of the next layers remain empty. The hydroxidometalate layer can be seen as isolated [Ir(OH)6]2− octahedra, which are embedded in a honeycomb net of alkali metal cations. Temperature‐dependent magnetic measurements revealed paramagnetic behavior with an effective moment of 1.9 μB per iridium ion. The thermal decomposition of Na2[Ir(OH)6] in air starts at about 220 °C and results in pure Na2IrO3. [ABSTRACT FROM AUTHOR]

In this study, wettability behavior of B4C substrate as well as B4C/crystalline rice husk ash and B4C/amorphous rice husk ash substrates with two aluminum alloys were studied. The electrical resistivity, thermal expansion coefficients, and thermal diffusivity of bilayer Al/B4C/rice husk ash composite fabricated by one-step pressureless infiltration were measured and the obtained data were systemically analyzed using the Taguchi method and analysis of variance. Boron carbide substrates after addition of amorphous or crystalline rice husk ash display good wettability with molten aluminum alloys. The results show that, electrical resistivity of Al/B4C/rice husk ash composites is mainly influenced by initial preform porosity, while the coefficient of thermal expansion of composites is determined by the chemical composition of infiltrated alloys. The measured values for coefficient of thermal expansion (10.5 × 10−6/℃) and electrical resistivity (0.60 × 10−5 Ω.m) of Al/B4C/rice husk ash composites, fabricated according to analysis of variance's optimal conditions are in good agreement with those of the projected values (11.02 × 10−6/℃ and 0.65 × 10−5 Ω.m, respectively). The difference between the corresponding values obtained from verification tests and projected values, for electrical resistivity and coefficient of thermal expansion are less than 5%. Finally, as a material selection approach, the strengths and weaknesses of the composites have been graphed in the form of radar diagrams. [ABSTRACT FROM AUTHOR]

BaAg2Cu[VO4]2 contains Cu(II) S=1/2 ions on a distorted two-dimensional triangular lattice interconnected via non-magnetic [VO4] entities. DFT band structure calculations, quantum Monte-Carlo simulations, and high-field magnetization measurements show that the magnetism of this compound is determined by a superposition of ferromagnetic (FM) and antiferromagnetic (AFM) uniform spin-1/2 chains with nearest neighbor exchange couplings of JFM=−19 K and JAFM=9.5 K (A. Tsirlin, A. Möller, B. Lorenz, Y. Skourski, H. Rosner, Phys. Rev. B 85 (2012) 014401). Here we report the study of BaAg2Cu[VO4]2 by high-field/frequency electron spin resonance (HF-ESR) and nuclear magnetic resonance (NMR) spectroscopies, which probe the local magnetic properties. In the HF-ESR measurements, we observe an anisotropic ESR spectrum typical for the Cu(II) ions and determine the g-tensor, g||=2.38 and g⊥=2.06. Moreover, we see a substantial change in the spectral shape of the ESR lines at low temperatures indicating the presence of short range magnetic correlations. The analysis of the low-temperature ESR spectra shows that its peculiar structure is due to the development of the anisotropic internal fields corresponding to FM and AFM correlations in the respective Cu spin chains. In the NMR spectra the signals from 51V nuclei in the two types of chains were identified. The analysis of the temperature evolution of these signals strongly supports the ESR findings on the occurrence of two types of Cu chains. Altogether, the HF-ESR and NMR results confirm theoretical predictions of the superposition of FM and AFM Cu(II) spin-1/2 chains in the studied material. [ABSTRACT FROM AUTHOR]