Search results for " local structure"

Average versus local structure in K2NiF4-type LaSrAlO4: direct experimental evidence of local cationic ordering

2012

The long-range ordering of a crystalline material can be accurately determined by analyzing the Bragg intensities and positions. In contrast, direct observation of short-range ordering in crystalline materials, which is increasingly considered of fundamental importance to unravel the structure-property relationships that underpin their technological applications, is a challenging task. In this study we have investigated the structure of LaSrAlO4, a representative example of compounds with the K2NiF4-type structure. By the combined use of synchrotron and neutron diffraction, pair distribution function analysis, Al-27 MQMAS NMR and atomistic simulations we have highlighted differences between…

Chapter 8: EPR in glass ceramics

2019

The development of novel materials requires a profound understanding of the relationship between a material's performance and its structural properties. Electron paramagnetic resonance (EPR) is a well-established technique for a direct detection and identification of paramagnetic defects in solids. This chapter provides an overview of the applicability of continuous wave EPR spectroscopy in the studies of glass ceramics focusing on transition metal (Mn2 +, Cu2 +, Cr3 +) and rare earth (Gd3 +, Eu2 +, Er3 +, Yb3 +) ion local structure analysis. EPR spectra features of the above-mentioned paramagnetic probes in glasses and glass ceramics are compared and discussed in detail. The chapter also s…

Local structure of the supported Keggin and Wells-Dawson heteropolyacids and its consequence on their (photo)catalytic activity

2018

Local structure of ball-milled LaNi5 hydrogen storage material by Ni K-edge EXAFS

2010

Abstract Local structure of the nanostructured LaNi5 hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a …

Spectroscopic and structural characterization of pure and FeCl3-containing tri-n-butyl phosphate

2014

The spectroscopic properties and liquid structure of pure tri-n-butyl phosphate (TBP) and FeCl3/TBP solutions have been investigated by Uv–Vis and Raman spectroscopies, X-ray diffraction and conductometry. Uv–Vis and Raman spectra, supported by conductometric measurements, consistently indicate that the solubilized salt is present mostly as TBP n [FeCl3 − n ] n+ and FeCl4 − complex ions due to specific interaction with the TBP phosphate group. Thanks to this interaction, a high amount of salt (up to 13 % w/w) can be dissolved despite the relatively low dielectric constant of TBP. The X-ray diffractogram of pure TBP has been interpreted in terms of three main contributions which can be attri…