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Magnetic field dependent neutron powder diffraction studies of Ru{sub 0.9}Sr{sub 2}YCu{sub 2.1}O{sub 7.9}
Temperature and magnetic field dependent neutron diffraction has been used to study the magnetic order in Ru{sub 0.9}Sr{sub 2}YCu{sub 2.1}O{sub 7.9}. The appearance of (1/2, 1/2, 1/2), (1/2, 1/2, 3/2), and (1/2, 1/2, 5/2) peaks below T{sub M}=140 K manifests the antiferromagnetic order. Neutron diffraction patterns measured in applied magnetic fields from 0 to 6 T show the destruction of the antiferromagnetic order with increasing field. There is no evidence of spontaneous or field-induced long range ferromagnetic order. This latter result contradicts the vast majority of other experimental observations for this system.
Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.
Towards a robust ad hoc data correction approach that yields reliable atomic pair distribution functions from powder diffraction data
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Grain size and structure distortion characterization of α-MgAgSb thermoelectric material by powder diffraction
Nanostructuring, structure distortion and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg 0.97 Sb 0.99 , with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. In this work, we report the average grain size of 24-28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron X-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg 0.97 Sb 0.99 .
Magnetic structure of the quasi-one-dimensional L a 3 Os O 7 as determined by neutron powder diffraction
Insulating 5d 3 La 3 OsO 7 and the isostructural hole-doped analog La 2.8 Ca 0.2 OsO 7 that feature pseudo-one-dimensional zigzag chains of corner-sharing OsO 6 octahedra were synthesized and their magnetic and electrical transport properties characterized. Both of these compounds are insulating antiferromagnets. Moreover, for long range magnetic order between the antiferromagnetic chains we determined with a propagation vector k = 1/2,1/2,1 and T N = 45 and 33 K the parent and doped materials. An Os 5+ moment of 1.7(1)μ B for La 3 OsO 7 and 1.2(2)μ B for La 2.8 Ca 0.2 OsO 7 is refined. The long range magnetic structure is compared to the isostructural compounds La 3 RuO 7 and La 3 MoO 7 , both of which adopt different magnetic structures.
Materials synthesis, neutron powder diffraction, and first-principles calculations of (Mo x Sc 1–x ) 2 AlC i–MAX phase used as parent material for MXene derivation
Research on low-dimensional materials has increased drastically in the last decade, with the discovery of two-dimensional transition metal carbides and nitrides (MXenes) produced by atom-selective chemical etching of laminated parent M n+1 AX n (MAX) phases. In this study, we apply density functional theory and subsequent materials synthesis and analysis to explore the phase stability and Mo/Sc intermixing on the M site in the chemically ordered quaternary i-MAX phase (Mo x Sc 1-x ) 2 AlC. Transmission electron microscopy confirms the theoretical predictions of preferential in-plane ordering of Mo and Sc, with the highest crystal quality obtained for the ideal Mo:Sc ratio of 2:1 (predicted as the most stable), as well as a retained i-MAX structure even for an increased relative Sc content, with Sc partially occupying Mo sites. The results are supported by refined neutron diffraction data, which show space group C2/c (no. 15), and a C occupancy of 1. Subsequent chemical etching produces MXene for x=0.66, while for x=0.33 and 0.5 no MXene is observed. These results demonstrate that a precise control of the i-MAX composition is crucial for derivation of MXene, with a MXene quality optimized for a Mo:Sc ratio of 2:1 with minimal intermixing between Mo and Sc.
SrRietveld: a program for automating Rietveld refinements for high-throughput powder diffraction studies
Abstract not provided
Solving complex open-framework structures from X-ray powder diffraction by direct-space methods using composite building units
Abstract not provided
Investigating temperature-induced structural changes of lead halide perovskites by in situ X-ray powder diffraction
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Real-time powder diffraction studies of energy materials under non-equilibrium conditions
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Crystal structures of two magnesium citrates from powder diffraction data
Abstract not provided
Study of Kinetics of Solid Phase Transition in Tetracosane С{sub 24}Н{sub 50} by High-Resolution Synchrotron X-Ray Powder Diffraction
Using the small-angle synchrotron X-ray diffraction method at the research facility “BELOK” of the Kurchatov synchrotron radiation source at the NRC Kurchatov Institute, it was shown that the first-order solid phase transition in tetracosane C{sub 24}H{sub 50} passes according to a heterogeneous mechanism in a narrow temperature range ΔT ~ 1 K in accordance with the theory of diffuse phase transitions.
The Certification of Standard Reference Material 1979: Powder Diffraction Line Profile Standard for Crystallite Size Analysis
Abstract not provided