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Title: Phase identification and structure investigation of novel quaternary rare-earth substituted titanates

Abstract

Novel quaternary lanthanide-substituted oxides of stoichiometry LnxY2-xTi2O7 (where Ln is lanthanum, neodymium, samarium, gadolinium, or ytterbium) were prepared by traditional high-temperature, solid-state techniques and characterized by X-ray powder diffraction. Samples with nominal values of x up to 1.0 were attempted. The well-studied ternary cubic pyrochlore compound yttrium titanium oxide (Y2Ti2O7, space group Fd-3m, Z = 8), served as a parent structural framework in which Ln3+ cations were substituted on the Y3+ site. Laboratory-grade X-ray powder diffraction data revealed pure quaternary pyrochlore phases for LnxY2-xTi2O7 with x ≤ 0.2. Pyrochlore phase purity was verified by Rietveld analysis using high-resolution synchrotron X-ray powder diffraction data when x ≤ 0.2, however, for La3+ substitution specifically, pure quaternary pyrochlore formed at x<0.1. Band gap energies on selected samples were determined using optical diffuse reflectance spectroscopy and showed that these materials can be classified as electrical insulators with indirect band gap energies around 3.7 eV.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
UNIVERSITY
OSTI Identifier:
1404971
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 256; Journal Issue: C
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Aldridge, James D., Womick, Jordan M., Rosmus, Kimberly A., Weiland, Ashley, Aitken, Jennifer A., and Polvani, Deborah A. Phase identification and structure investigation of novel quaternary rare-earth substituted titanates. United States: N. p., 2017. Web. doi:10.1016/j.jssc.2017.08.030.
Aldridge, James D., Womick, Jordan M., Rosmus, Kimberly A., Weiland, Ashley, Aitken, Jennifer A., & Polvani, Deborah A. Phase identification and structure investigation of novel quaternary rare-earth substituted titanates. United States. doi:10.1016/j.jssc.2017.08.030.
Aldridge, James D., Womick, Jordan M., Rosmus, Kimberly A., Weiland, Ashley, Aitken, Jennifer A., and Polvani, Deborah A. 2017. "Phase identification and structure investigation of novel quaternary rare-earth substituted titanates". United States. doi:10.1016/j.jssc.2017.08.030.
@article{osti_1404971,
title = {Phase identification and structure investigation of novel quaternary rare-earth substituted titanates},
author = {Aldridge, James D. and Womick, Jordan M. and Rosmus, Kimberly A. and Weiland, Ashley and Aitken, Jennifer A. and Polvani, Deborah A.},
abstractNote = {Novel quaternary lanthanide-substituted oxides of stoichiometry LnxY2-xTi2O7 (where Ln is lanthanum, neodymium, samarium, gadolinium, or ytterbium) were prepared by traditional high-temperature, solid-state techniques and characterized by X-ray powder diffraction. Samples with nominal values of x up to 1.0 were attempted. The well-studied ternary cubic pyrochlore compound yttrium titanium oxide (Y2Ti2O7, space group Fd-3m, Z = 8), served as a parent structural framework in which Ln3+ cations were substituted on the Y3+ site. Laboratory-grade X-ray powder diffraction data revealed pure quaternary pyrochlore phases for LnxY2-xTi2O7 with x ≤ 0.2. Pyrochlore phase purity was verified by Rietveld analysis using high-resolution synchrotron X-ray powder diffraction data when x ≤ 0.2, however, for La3+ substitution specifically, pure quaternary pyrochlore formed at x<0.1. Band gap energies on selected samples were determined using optical diffuse reflectance spectroscopy and showed that these materials can be classified as electrical insulators with indirect band gap energies around 3.7 eV.},
doi = {10.1016/j.jssc.2017.08.030},
journal = {Journal of Solid State Chemistry},
number = C,
volume = 256,
place = {United States},
year = 2017,
month =
}
  • The purpose of this work was to investigate the effect of different regimes of quenching with cooling rates of approx. 10/sup 2/ and 10/sup 5/ K/sec on the phase composition of rare-earth mono- and dititanates, as well as the possibility of formation of glasses at the nonvariant points (eutectic and peritectic) of the binary systems TiO/sub 2/-Ln/sub 2/O/sub 3/ (Ln-La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc). For compounds of the types Ln/sub 2/TiO/sub 5/ and Ln/sub 2/Ti/sub 2/O/sub 7/ (Ln-La...Lu, Y, Sc) there is a tendency for a structure with amore » higher symmetry to form as the ionic radius of the lanthanide decreases and the rate of quenching increases. The use of ultrarapid quenching expanded the region of existence of the cubic structure of the fluorite type to Tb/sub 2/TiO/sub 5/ and the structure of the pyrochlore type up to Sm/sub 2/Ti/sub 2/O/sub 7/. Ultrarapid quenching of compounds with the composition Ln/sub 4/Ti/sub 9/O/sub 24/ led to a transition into the amorphous state.« less
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