A. Senyshyn

Scientific Review: The Structure Powder Diffractometer SPODI

The structure powder diffractometer SPODI at FRM II is a common project of Darmstadt University of Technology, Ludwig-Maximilians University Munich, and Technische Universität München. The main objectives of the instrument are to achieve a high Q-resolution and to provide a versatile and powerful sample environment. In addition to common applications of high-resolution powder diffraction to determine crystallographic and magnetic structures, the diffractometer SPODI is developed particularly for materials science applications. Prior to the construction, individual components as well as the whole instrument have been simulated by Monte Carlo technique applying the McStas software [1]. Results of these studies have been reported in [2,3].

Crystal structure, thermal expansion and conductivity of anisotropic La1−xSrxGa1−2xMg2xO3−y (x=0.05, 0.1) single crystals

Abstract Crystal structure and anisotropy of the thermal expansion of single crystals of La 1− x Sr x Ga 1−2 x Mg 2 x O 3− y ( x =0.05 and 0.1) were measured in the temperature range 300–1270xa0K. High-resolution X-ray powder diffraction data obtained by synchrotron experiments have been used to determine the crystal structure and thermal expansion. The room temperature structure of the crystal with x =0.05 was found to be orthorhombic ( Imma , Z =4, a =7.79423(3)xa0A, b =5.49896(2)xa0A, c =5.53806(2)xa0A), whereas the symmetry of the x =0.1 crystal is monoclinic ( I 2 /a , Z =4, a =7.82129(5)xa0A, b =5.54361(3)xa0A, c =5.51654(4)xa0A, β =90.040(1)°). The conductivity in two orthogonal directions of the crystals has been studied. Both, the conductivity and the structural data indicate three phase transitions in La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 2.92 at 520–570xa0K ( Imma – I 2 /a ), 770xa0K ( I 2 /a – R 3 c ) and at 870xa0K ( R 3 c – R- 3 c ), respectively. Two transitions at 770xa0K ( I 2 /a – R 3 c ) and in the range 870–970xa0K ( R 3 c – R- 3 c ) occur in La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.85 .

Synthesis, Characterization, and Comparison of Electrochemical Properties of LiM0.5Mn1.5O4 (M = Fe , Co, Ni) at Different Temperatures

LiM 0.5 Mn 1.5 O 4 (M = Fe, Co, Ni) normal spinel oxides were prepared by a citric acid assisted Pechini synthesis with different thermal treatments and compared with respect to their electrochemical performance as cathodes in lithium-ion batteries. Characterization methods include X-ray diffraction, neutron diffraction, inductively coupled plasma optical emission spectroscopy analysis, and scanning electron microscopy. While LiM 0.5 Mn 1.5 O 4 samples crystallize for M = Fe and Co with the 3d cation-disordered cubic spinel-like structure (Fd3m space group), the 600°C annealed LiM 0.5 Mn 1.5 O 4 shows a partially ordered structure (belonging to the P4 3 32 space group). The absolute discharge capacity is slightly higher for the Ni-doped samples in comparison with the Co-and Fe-doped spinels. 1000°C annealed samples show an improved cyclability in comparison with the 600°C annealed samples. At elevated temperatures, Co- and Fe-doped samples show much faster degradation in comparison with the Ni-doped sample. The responsible mechanisms are discussed.

Crystal structure of ZnWO 4 scintillator material in the range of 3-1423 K

The behaviour of the crystal structure of ZnWO(4) was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300xa0K. Thermal analysis showed the samples melting around 1486xa0K upon heating and subsequent solidification at 1442xa0K upon cooling. Therefore, the structure was also investigated at 1423xa0K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO(4) at low temperatures were parametrized on the basis of the first order Grüneisen approximation and a Debye model for an internal energy. The expansivities along the a-xa0and b-axes adopt similar values and saturate close to 8 × 10(-6)xa0K(-1), whereas the expansion along the c-axis is much smaller and shows no saturation up to 300xa0K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur.

Lattice dynamics and thermal properties of Ca W O 4

Thermodynamic properties of

Low-temperature crystal structure, specific heat, and dielectric properties of lithium tetraborate Li2B4O7

mathrm{Ca}mathrm{W}{mathrm{O}}_{4}

Chapter 242 Perovskite-Type Aluminates and Gallates

were studied using the GULP code incorporating semiclassical simulations based on quasiharmonic lattice dynamics and static lattice minimisation methods. Free energy minimization along with so called ``relax fitting was used to obtain the parameters characterising the interatomic interaction potential. From analyses of the calculated and experimental cell sizes, thermal expansion coefficients, elastic constants, phonon density of states, heat capacity, entropy, and Gruneisen parameters it is concluded that quasiharmonic lattice dynamics give a good description of these properties of

Anomalous thermal expansion in rare-earth gallium perovskites : a comprehensive powder diffraction study

mathrm{Ca}mathrm{W}{mathrm{O}}_{4}

Computational study of LnGaO3 (Ln = La–Gd) perovskites

at temperatures up to

Degenerate rhombohedral and orthorhombic states in Ca-substituted Na0.5Bi0.5TiO3

800phantom{rule{0.3em}{0ex}}mathrm{K}