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The excellent photon beam quality provided at 3rd generation synchrotron sources opens up new opportunities in materials chemistry using X-ray powder diffraction. Techniques that cover the range from very detailed structure analysis to the observation of rapid structural changes during chemical reactions in real time have become viable. Recent experiments carried out at the High Resolution Powder Diffraction Beamline P02.1 at PETRA III (DESY) demonstrate how to effectively exploit the highly collimated, very intense X-rays of high energies for chemistry and materials science. Two studies are described in detail, which illustrate the outstanding performance of the instrument: the determination of charge density distributions from powder patterns, and atomic rearrangements followed in situ during the formation of metallic and oxide nanoparticles in solution. [ABSTRACT FROM AUTHOR]

In a powder diffraction pattern one measures the intensity of Miller-indexed Bragg peaks versus the wavevector transfer sinθ/λ. With increasing wavevector transfer the density of occurrence of Bragg peaks increases while their intensity decreases until they vanish into the background level. The lowest possible background level is that due to Compton scattering from the powder. A powder diffraction instrument has been designed and tested that yields this ideal low-background level, obtainable by having the space between sample and detector all in vacuum with the entrance window so far upstream that scattering from it is negligible. To minimize overlap of Bragg peaks the combination of fine collimation of synchrotron radiation, a thin cylindrical sample and a high-resolution imaging plate detector is taken advantage of. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis method offers an environmentally benign way of synthesizing Li-ion battery materials with strong control of particle size and morphology, and thereby also the electrochemical performance. Here we present an in depth investigation of the crystal structure, microstructure and electrochemical properties of hydrothermally synthesized LiMn2O4, which is a widely used cathode material. A range of samples were synthesized by a simple, single-step hydrothermal route, and the products were characterized by elaborate Rietveld refinement of powder X-ray diffraction data, electron microscopy and electrochemical analysis. A distinct bimodal crystallite size distribution of LiMn2O4 was formed together with a Mn3O4 impurity. At high LiOH concentration the layered LixMnyO2 phase was formed. The crystallite sizes and impurity weight fractions were found to be highly synthesis dependent, and the amount of spinel impurity phase was found to correlate with deterioration of the electrochemical performance. The Mn3O4 phase can be very difficult to quantify in standard powder X-ray diffraction and due to peak overlap and X-ray fluorescence impurity levels of more than 10% are easily hidden. Furthermore, the spinel LiMn2O4 phase can easily be mistaken for the layered LixMnyO2 phase. The present study therefore highlights the importance of thorough structural characterization in studies of battery materials. [ABSTRACT FROM AUTHOR]

TiO2@SnO2 hybrid nanocomposites were successfully prepared in gram scale using a dual-stage hydrothermal continuous-flow reactor. Temperature and pH in the secondary reactor were found to selectively direct nucleation and growth of the secondary material into either heterogeneous nanocomposites or separate intermixed nanoparticles. At low pH, 2 nm rutile SnO2 nanoparticles were deposited on 9 nm anatase TiO2 particles; the presence of TiO2 was found to suppress formation of larger SnO2 particles. At high pH SnO2 formed separate particles and no deposition on TiO2 was observed. Ball-milling of TiO2 and SnO2 produced no TiO2@SnO2 composites. This verifies that the composite particles must be formed by nucleation and growth of the secondary precursor on the TiO2 . High concentration of secondary precursor led to formation of TiO2 particles embedded in aggregates of SnO2 nanoparticles. The results demonstrate how nanocomposites may be produced in high yield by green chemistry., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Understanding nanoparticle-formation reactions requires multi-technique in situ characterisation, since no single characterisation technique provides adequate information. Here, the first combined small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering (WAXS)/total-scattering study of nanoparticle formation is presented. We report on the formation and growth of yttria-stabilised zirconia (YSZ) under the extreme conditions of supercritical methanol for particles with Y(2)O(3) equivalent molar fractions of 0, 4, 8, 12 and 25 %. Simultaneous in situ SAXS and WAXS reveals a quick formation (seconds) of sub-nanometre amorphous material forming larger agglomerates with subsequent slow crystallisation (minutes) into nanocrystallites. The amount of yttria dopant is shown to strongly affect the crystallite size and unit-cell dimensions. At yttria-doping levels larger than 8 %, which is known to be the stoichiometry with maximum ionic conductivity, the strain on the crystal lattice is significantly increased. Time-resolved nanoparticle size distributions are calculated based on whole-powder-pattern modelling of the WAXS data, which reveals that concurrent with increasing average particle sizes, a broadening of the particle-size distributions occur. In situ total scattering provides structural insight into the sub-nanometre amorphous phase prior to crystallite growth, and the data reveal an atomic rearrangement from six-coordinated zirconium atoms in the initial amorphous clusters to eight-coordinated zirconia atoms in stable crystallites. Representative samples prepared ex situ and investigated by transmission electron microscopy confirm a transformation from an amorphous material to crystalline nanoparticles upon increased synthesis duration., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)