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This study aims at investigating the role of the dielectric constant of polyols on the size and morphology of SrTiO 3 nanostructures and thereby its effect on the photocatalytic performance of the oxide. Herein, among the various available polyols, we have used ethylene glycol (EG), poly(ethylene glycol)-300 (PEG-300), and poly(ethylene glycol)-400 (PEG-400) for our study. The effect of polyols was also compared by taking water as the solvent instead of polyols. We discuss how a change in the synthetic methodology, i.e., change of the solvent, affects the defects, crystallite size, and nature of the facets. We observed that the particle size decreased with an increase in the dielectric constant of the solvent (water and polyols). We also observed that the shape (nanocubes with water, nanocuboids with PEG-400, edge-truncated nanocuboids with PEG-300, and hexagonal-shaped particles assembled to form a flower-like nanostructure with EG as solvent) and nature of the exposed facets were also affected by the dielectric constant of the solvent. The top exposed facet of the synthesized SrTiO 3 nanostructures was observed to be [001] (for SrTiO 3 nanostructures synthesized using different solvents) with [011̅ ] facet, as observed for the sample synthesized using EG and PEG-300 as the solvent. The effect of size and shape on their photocatalytic performance (during both photodegradation of Rhodamine B (RhB) and hydrogen evolution) was also evaluated.

The article presents a concise review of our investigations on the preferred transition paths followed as well as high-pressure-induced structural changes in nanocrystalline rare-earth sesquioxides that include Y2O3, Sm2O3, Gd2O3, Eu2O3, Dy2O3, Ho2O3, and Yb2O3. The starting phase in all samples was predominantly cubic, as characterized using X-ray diffraction and Raman spectroscopy. The pressure-induced structural changes were primarily tracked via changes in phonon modes in the Raman spectra. The structural transition sequences demonstrated behaviors differing from the polycrystalline trends usually observed; however, it was interesting to note that the onset pressures and subsequent shifts in the phonon modes followed a trend similar to the unpressurized samples when observed with respect to the f-electron number. The mode Grüneisen parameters were estimated from the high-pressure data, which indicated a swifter response to external stimuli as the particle size reduced below an average of 50 nm. It was also inferred that the presence of traces of disordered/nonstoichiometric material directly affected the structural transition sequence. A summary of the results and the mechanisms leading to such structural transitions is discussed.

Fast-anion-conducting glasses in the system xPbF2:(1-x)B2O3 have been synthesized and analysed by thermal, electrical and spectroscopic techniques. The ionic conductivity ( sigma ) of these glasses is measured as a function of temperature and chemical composition by the complex impedance method and the results indicate that the conduction of fluorine as charge carriers is governed by activation energy alone. Infrared and X-ray photoelectron spectroscopy studies have provided evidence for fluorine participation in the berate network. Further, the compositional dependence of X-ray photoelectron F 1s spectra indicates that fluorine is incorporated predominantly as B-O-F and Pb-O-F bonds in the oxide network at high B2O3 and PbF2 content respectively. The spectroscopic results obtained are discussed in relation to anionic conduction.

This study focuses on relating the structure with their properties and activity and carries out a comparative study amongst the three members of the Sr-Ti-O system for photocatalytic hydrogen evolution....

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The nanocrystalline rare earth sesquioxides Dy2O3, Gd2O3 and Y2O3 have been investigated for anharmonic effects in the temperature range 80–440 K using Raman spectroscopy. These samples were cubic in structure under ambient conditions with particle sizes in nano‐range. The predominant Tg + Ag phonon modes of the samples primarily exhibited phonon softening in the investigated temperature range. However, the line width variations clearly reflected the variations in the effects of anharmonicity on these samples, and the related anharmonic constants were estimated. The mode Grüeneisen parameters required for these studies were deduced from our own high‐pressure data for these samples reported earlier. The line width variations for these samples were found to display similar trends; however, their magnitudes were indicative of the factors that are expected to contribute to the variation in phonon behaviour. Copyright © 2017 John Wiley & Sons, Ltd.

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