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Title: X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates

Abstract

Laboratory and synchrotron x-ray powder diffraction were used to investigate the structural modifications that occur upon indium doping of tin pyrophosphate. The data collected under air, vacuum, and inert gas sample environments at temperatures (T) from 50 °C to 300 °C show that regardless of the In-doping level (0 ≤ x ≤ 0.18) all InxSn1-xP2O7 samples are isomorphic (have the same P a -3 cubic crystal structure) at all temperatures and under all the conditions investigated. The cubic lattice parameter (a) increases linearly with T at all doping levels, but the “a vs. x|T“ isotherms exhibit a robust peak at x = 0.1 when data are collected on samples measured in air. On the other hand, Rietveld refinements against data collected on InxSn1-xP2O7 samples yield values of OO bond lengths and POP bond angles that show no major changes at x = 0.1 at any temperature. This is significant, as the Sn0.9In0.1P2O7 (x = 0.1) compound is known to exhibit the highest proton conductivity within the series, but the microscopic details responsible for the increased proton conductivity are not understood. Finally, the peak observed in the “a vs. x|T“ curves vanishes if the measurements are taken on samples kept eithermore » under vacuum or in an inert gas environment. This is a remarkable behavior as it lends further support to our hypothesis that a key microscopic feature responsible for the large proton conductivity of the Sn0.9In0.1P2O7 compound is the enlargement of the lattice constant at x = 0.1.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1409640
Report Number(s):
BNL-114692-2017-JA¿¿¿
Journal ID: ISSN 0254-0584
DOE Contract Number:
SC0012704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Chemistry and Physics; Journal Volume: 196; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Botez, Cristian E., Martinez, Heber, and Morris, Joshua L. X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates. United States: N. p., 2017. Web. doi:10.1016/j.matchemphys.2017.04.058.
Botez, Cristian E., Martinez, Heber, & Morris, Joshua L. X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates. United States. doi:10.1016/j.matchemphys.2017.04.058.
Botez, Cristian E., Martinez, Heber, and Morris, Joshua L. 2017. "X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates". United States. doi:10.1016/j.matchemphys.2017.04.058.
@article{osti_1409640,
title = {X-ray diffraction investigations of structural modifications in In-doped tin pyrophosphates},
author = {Botez, Cristian E. and Martinez, Heber and Morris, Joshua L.},
abstractNote = {Laboratory and synchrotron x-ray powder diffraction were used to investigate the structural modifications that occur upon indium doping of tin pyrophosphate. The data collected under air, vacuum, and inert gas sample environments at temperatures (T) from 50 °C to 300 °C show that regardless of the In-doping level (0 ≤ x ≤ 0.18) all InxSn1-xP2O7 samples are isomorphic (have the same P a -3 cubic crystal structure) at all temperatures and under all the conditions investigated. The cubic lattice parameter (a) increases linearly with T at all doping levels, but the “a vs. x|T“ isotherms exhibit a robust peak at x = 0.1 when data are collected on samples measured in air. On the other hand, Rietveld refinements against data collected on InxSn1-xP2O7 samples yield values of OO bond lengths and POP bond angles that show no major changes at x = 0.1 at any temperature. This is significant, as the Sn0.9In0.1P2O7 (x = 0.1) compound is known to exhibit the highest proton conductivity within the series, but the microscopic details responsible for the increased proton conductivity are not understood. Finally, the peak observed in the “a vs. x|T“ curves vanishes if the measurements are taken on samples kept either under vacuum or in an inert gas environment. This is a remarkable behavior as it lends further support to our hypothesis that a key microscopic feature responsible for the large proton conductivity of the Sn0.9In0.1P2O7 compound is the enlargement of the lattice constant at x = 0.1.},
doi = {10.1016/j.matchemphys.2017.04.058},
journal = {Materials Chemistry and Physics},
number = C,
volume = 196,
place = {United States},
year = 2017,
month = 8
}
  • In a search for new luminescent biological probes, we synthesized calcium pyrophosphates doped with europium up to an atomic Eu/(Eu+Ca) ratio of 2%. They were prepared by coprecipitating a mixture of calcium and europium salts with phosphate. After heating at 900{sup o}C in air, two phases coexisted, identified as the {beta} calcium pyrophosphate form and EuPO{sub 4}. Heating near 1250{sup o}C in air, during the {beta}->{alpha} transformation, europium ions substitute for calcium ions in the {alpha} calcium pyrophosphate structure as demonstrated by the spectroscopic study. Europium ions with both valence states (divalent and trivalent) were observed in the samples. Followingmore » the synthesis procedure, partial reduction of Eu{sup 3+} took place even in an oxidizing atmosphere. The 0.5%-doped compound could serve as a sensitive probe in biological applications. Depending on the excitation wavelength, the luminescence occurs either in the red or in the blue regions, which discriminates it from parasitic signals arising from other dyes or organelles in live cells.« less
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  • Highlights: • We studied the evolutions of structure for TiO{sub 2} thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb{sub 0.1}Ti{sub 0.9}O{sub 2} is smaller than for pure TiO{sub 2} because doped Nb hinders the growth of the TiO{sub 2} grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO{sub 2} films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO{sub 2} which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methodsmore » were used to prepare Nb-doped TiO{sub 2} thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO{sub 2} by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming that niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb{sup 5+} ions into the lattice. The band gap energy of indirect transition of the TiO{sub 2} thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2.40 eV.« less
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