We report on the preparation and the X-ray crystal structure of colorless KSbGe3O9, its vibrational properties (Raman and infrared studies), and density functional theory (DFT) calculations. KSbGe3O9, grown by the high-temperature flux method from K2Mo4O13 flux, is thermally stable at least up to 1200 degrees C and is isostructural to the benitoite BaTiSi3O9 (space group P (6) over bar c2 (no. 188)). The hexagonal unit cell contains two formula units and the structure was refined to R1 = 0.0324 from single-crystal X-ray diffraction data. KSbGe3O9 is characterized with only one crystallographically independent Ge atom involved in three-member units [Ge3O9](6-) of regular germanate tetrahedra. The K+ ions are located in channels and, like Sb-V, are octahedrally surrounded by oxygen atoms. The KSbGe3O9 local structure and the planarity of Ge3O3 rings are also studied by a room-temperature vibrational investigation using non-polarized infrared and Raman spectroscopy. Both the infrared and Raman phonon modes have been assigned from the agreement observed between our experimental data and the corresponding DFT ones. In particular, two E'(TO) modes (both IR and Raman active) characterize the planarity of the Ge3O3 ring in the ab plane.

The RbSbGe3O9 compound, grown by the high-temperature solution technique from the Rb2Mo4O13 flux, crystallizes in the trigonal non-centrosymmetric space group P31c (no. 159). The structure was solved and refined from single-crystal X-ray diffraction data recorded at ambient temperature. The unit cell contains six formula units. The three-dimensional RbSbGe3O9 network is built with three-membered units [Ge3O9]6- of regular germanate tetrahedra involving three crystallographically independent Ge atoms. The Ge3O3 central rings located in the ab plane deviate only slightly from the planarity. Antimony SbV is octahedrally coordinated by oxygen, and rubidium (Rb+), which is surrounded by six oxygen atoms, is located in the channels of the 3-D network. The structure of RbSbGe3O9 containing both isolated SbO6 octahedra and Ge3O9 cyclic units is comparable but not isostructural to the benitoite type. The almost flat character of the Ge3O3 rings is also attested by the vibrational study at room temperature via non-polarized infrared and Raman spectroscopy.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

In the present work, we study the anharmonicity of the unfilled CoSb3 skutterudite from the pressure and temperature dependence of the Raman-active modes. A full assignment of the Raman-active modes of CoSb3 was performed for the first time. Significant changes in the Raman spectra are observed above 27 GPa and attributed to the insertion of antimony atoms within the cages under high external pressure. We report the lattice dynamics of SbCo4Sb12 by DFT calculations and find very low-energy optical modes due to the antimony guest atoms with the cage framework. We report the isothermal Gruneisen parameters of the Raman-active modes, which are larger and approach 2 for the highest energy modes. From analysis of the temperature and pressure dependence of the Raman-active modes, we found that the implicit volume contribution is the dominant contribution for the highest energy Raman-active modes, whereas both the implicit volume contribution and the explicit anharmonic contribution have the same magnitude for the other Raman-active modes.

GaAsO4 crystals were grown by a hydrothermal epitaxial process. Microcrystalline GaAsO4 powder was first synthesized by hydrothermal methods by using GaAs as a starting material in a sulfuric acid solvent under oxidizing conditions. Experimental conditions were optimized and the yield of the nutrient synthesis reached 88%. GaAsO4 powder was then used as the nutrient for growing GaAsO4 single crystals by epitaxy on (21¯0) oriented GaPO4, AlPO4 and GaAsO4 plates. Crystal growth was performed in a horizontal PTFE-lined autoclave divided into two parts using sulfuric acid as the solvent under a slow heating gradient. Hydrothermal conditions were optimized in order to improve the crystal quality. The influence of the nature and orientation of the seeds on the growth rate was studied. From the solubility curve, the solute supply ΔS as a function of temperature during the growth process was calculated. Transparent crystals were obtained with ΔS between 0.002 and 0.009mol/L. Large crystals (3.9×1.8×1.4cm3) of gallium arsenate were obtained. These crystals were cut into (21¯0), (010) and (001) plates. Mapping using Raman spectroscopy was performed in order to study the growth recovery on the seed. GaAsO4 crystals were characterized by infrared spectroscopy in order to quantify the amount of OH groups in the crystal structure. A low value of the absorption coefficient α at 3300cm−1 was measured 0.067cm−1 indicating a good crystal quality. Optical measurements were performed on GaAsO4 crystals by UV–vis–NIR spectrophotometry. Gallium arsenate exhibits the highest value of birefringence in the α-quartz group with Δn=0.033. The transmission in the spectral region above 250nm yields a bandgap of 5.85eV. Piezoelectric properties were measured on resonators. An electromechanical coupling coefficient of 20% was measured which is the highest in the α-quartz group. A quality factor QF of 3.2×1010 was obtained on a Y-cut plate. The C66 elastic constant was found to be 20GPa.

alpha-Quartz-type Ga1-xFexPO4 solid solutions (0.04 <= x <= 0.28) and pure GaPO4 and FePO4 end members were studied by X-ray diffraction (XRD) and Raman spectroscopy to investigate the influence of iron content on the GaPO4 structure, and to have a better understanding of the lattice dynamics of the Ga1-xFexPO4 solid solutions. The unit cell parameters and structural distortion (i.e. inter-tetrahedral bridging theta, and tetrahedral tilt delta angles) of Ga1-xFexPO4 solid solutions were found to vary linearly with the iron content. Coupled and decoupled vibrational modes were identified using Raman spectroscopy and the calculation of the localization entropy using density functional theory. The GaPO4 decoupled modes are centered at 98, 237, 365 and 183 cm(-1) and respectively assigned to E(TO1), E(TO5), E(TO7) and A(1), while the vibrational modes located between 400 and 1200 cm(-1) could be coupled. The coupled A(1) bending mode centered at 457 cm(-1) in pure alpha-GaPO4 was found to vary linearly as a function of iron content at room temperature. This mode could be therefore used to determine the iron content in Ga1-xFexPO4 solid solutions.

Freezing of water in hydrophilic nanopores (D=1.2  nm) is probed at the microscopic scale using x-ray diffraction, Raman spectroscopy, and molecular simulation. A freezing scenario, which has not been observed previously, is reported; while the pore surface induces orientational order of water in contact with it, water does not crystallize at temperatures as low as 173 K. Crystallization at the surface is suppressed as the number of hydrogen bonds formed is insufficient (even when including hydrogen bonds with the surface), while crystallization in the pore center is hindered as the curvature prevents the formation of a network of tetrahedrally coordinated molecules. This sheds light on the concept of an ubiquitous unfreezable water layer by showing that the latter has a rigid (i.e., glassy) liquidlike structure, but can exhibit orientational order.

It is well known that bismuth telluride (Bi 2 Te 3 ), its isomorphs (Bi 2 Se 3 and Sb 2 Te 3 ) and their alloys have the optimum bandgap (0.13 eV to 0.21 eV) for efficient solid state cooling applications around 300 K. Recently interesting work argued that the use of quantum well structures can enhance the figure of merit ZT as a result of the improvement of carrier charge density of state and the reduction of the thermal conductivity. However, for the production of such structures it is necessary to establish the optimum growth conditions and the doping levels of thin films based on Bi 2 Te 3 and its isomorphs. In this paper we report on the growth characteristics of Bi 2 Te 3 ternary alloys (even quaternary) thin films elaborated by the Hot Wall Epitaxy (HWE) technique. Ternary alloys based on bismuth telluride have been deposited as thin films on silicon and silica substrates. Hot Wall Epitaxy have been demonstrated to be a suitable technique in chalcogenides growth. These films are formed in a closed chamber, that make possible to keep substrates at relatively high temperature T s without selective loss of individual components from condensate. Experimental procedures, such as substrate and source materials preparations, have been described in our previous publications. Thin films obtained are well oriented (001) and have block single-crystal structure. These films were studied by microstructural investigations and electrical measurements (electrical conductivity σ, Hall coefficient R H and Hall mobility μ n ) in the temperature range from liquid nitrogen to 570 K.

Nanocrystalline Zn1−xFexO (where x=0, 0.01 and 0.02) powders were successfully synthesized by a precipitation method from citrate-modified zinc nitrate solution. X-ray powder diffraction, Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy were used to study the structural properties. The optical properties were determined by UV–vis spectrophotometer and luminescent spectrometer. In this study, the optical band gap of nanocrystalline ZnO powder increased from 3.170eV to 3.214eV when the Fe concentration in the solution was increased up to 2mol. %.

In this study, the use of combustion synthesis for immobilization of 14C was considered. Ceramic matrices have been prepared by this method using two different devices: one non-conventional with preheating of the samples and the other conventional device where ignition was produced thanks to tungsten filament. These two devices gave rise to different mechanisms of reactions involving different amounts of unreacted carbon graphite inside the matrix. The SHS samples were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Zinc oxide (ZnO) and aluminium doped ZnO nanoparticles with grain size in the nanometer range have been successfully synthesized by alkali precipitation method. The grain size and morphology of nanoparticles have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The smallest size of about 25–30nm with a spherical shape has been measured from 10mol% aluminium doped ZnO. The optical band gap of undoped ZnO nanoparticles increases from 3.16 to 3.20eV when increasing the aluminium concentration to 10mol% into solution.

The reaction of 3,3’-diisopropyl-5,5’-bipyrazole with 4-fluoronitrobenzene allows to only one of the three regioisomers : 1,1'-bis(4-nitrophenyl)-5,5'-diisopropyl-3,3'-bipyrazole. Its crystal structure is confirmed by X ray crystallography. It crystallizes in space group P21/c with two asymmetic units C12H12N3O2 per molecule.

The structural properties of the Ce delta Fe4-xNixSb12 series with 0.06 <= delta <= 0.72 have been determined by neutron powder diffraction in the temperature range 10-300 K. Large isotropic atomic displacement parameters are observed for the cerium atom throughout the series, however with two distinct origins. The first term, purely dynamic, is well described as an Einstein oscillator and has essentially no dependence with the filling fraction 8 and the lattice parameter. A vibrational frequency of 55(2) cm(-1) fitted the experimental data in the entire phase diagram. The second contribution is essentially static and well evidenced by a large residual displacement parameter extrapolated to 0 K. This latter term does depend strongly on 3 and is maximum at around delta = 0.5, representing almost 50% of the room temperature value. A number of structural changes of the Sb sublattice are correlated with the disorder of Ce as well as disorder on the Fe/Ni sublattice.

A new 3,3’-bipyrazole derivative was prepared and regioselectively dibenzylated to afford a target product 1,1’-dibenzyl-5,5’-diisopropyl-3,3’-bipyrazole which clearly established from spectroscopic data (IR, 1H and 13C NMR, mass spectrometry and elemental analysis) and X-ray crystallography.

By using differential thermal analysis, metallography, microprobe analysis and X-ray powder diffraction, the Ti5Si3–Tb5Si3 section of the Ti–Tb–Si system was constructed. The section was shown to be quasibinary of eutectic type. The eutectic coordinates were determined to be 1655°C and ∼43at.% Tb.

Partially filled skutterudites have attracted a lot of attention in the last years notably because these compounds can be synthesised in large composition ranges and can easily be substituted. Our study is focussed on the series Ce,Fe4. .Ni,Sh12 with the aim to understand how the Ce filling fraction influences the electronic and thermal properties. Two ‘main results emerge from the present work. In the series with y-4132x13, it appears that the network can’t fully accommodate the cerium content for high values of y, resulting in metallic-type electronic transport properties. Secondly, thermal expansions measured by neutron diffraction show that the Dehye temperature is reduced with increasing cerium content supporting a more complex picture than originally thought.

Partially filled skutterudites have attracted a lot of attention in the last years notably because these compounds can be synthesised in large composition ranges and can easily be substituted. Our study is focussed on the series Ce/sub y/Fe/sub 4-x/Ni/sub x/Sb/sub 12/ with the aim to understand how the Ce filling fraction influences the electronic and thermal properties. Two main results emerge from the present work. In the series with y=4/3-2/spl times//3, it appears that the network can't fully accommodate the cerium content for high values of y, resulting in metallic-type electronic transport properties. Secondly, thermal expansions measured by neutron diffraction show that the Debye temperature is reduced with increasing cerium content supporting a more complex picture than originally thought.

Partially filled skutterudites have attracted a lot of attention in the last years notably because these compounds can be synthesised in large composition ranges and can easily be substituted. Our study is focussed on the series CeyFe4-xNixSb12 with the aim to understand how the Ce filling fraction influences the electronic and thermal properties. Two main results emerge from the present work. In the series with y=4/3-2×/3, it appears that the network can't fully accommodate the cerium content for high values of y, resulting in metallic-type electronic transport properties. Secondly, thermal expansions measured by neutron diffraction show that the Debye temperature is reduced with increasing cerium content supporting a more complex picture than originally thought.