skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Structural changes of (K,Gd){sub 2}Ta{sub 2}O{sub 7} pyrochlore at high pressure

Abstract

The structure of K-bearing tantalate pyrochlore (K{sub 2-x}Gd{sub x})Ta{sub 2}O{sub 6+x}(x{approx}0.4) was studied at high pressures using in situ X-ray diffraction and Raman scattering methods. Experimental results indicated that (K{sub 2-x}Gd{sub x})Ta{sub 2}O{sub 6+x}(x{approx}0.4) retains the pyrochlore structure up to 40 GPa, but partial amorphization occurred at pressures above 23 GPa. The amorphous phase was also confirmed in the quenched sample by means of transmission electron microscopy. The tantalate pyrochlore lattice is more stable than pyrochlore compounds in other systems, such as rare earth titanates, zirconates and stannates. The structural stability of pyrochlore tantalate may be mainly related to the size ratio of cations on the 16d and 16c sites in the lattice. - Graphical Abstract: In the pyrochlore tantalate, K and Gd co-occupy the 16d site and Ta is on the 16c site and forming octahedra with nearby anions. The pyrochlore tantalate is quite resistant to high pressure even when the structure is partially amorphized. Highlights: > In situ XRD measurements revealed that (KGd){sub 2}Ta{sub 2}O{sub 7} pyrochlore is much stable than other pyrochlore oxides at high pressures. > Pyrochlore tantalate can be partially amorphized at high pressures. > The enhanced phase stability of tantalate pyrochlore is due tomore » the large size difference of cations.« less

Authors:
 [1]; ;  [1];  [1];  [2]
  1. Department of Geological Science, The University of Michigan, Ann Arbor, MI 48109 (United States)
  2. Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185 (United States)
Publication Date:
OSTI Identifier:
21580256
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 184; Journal Issue: 9; Other Information: DOI: 10.1016/j.jssc.2011.06.040; PII: S0022-4596(11)00368-9; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AMORPHOUS STATE; PHASE STABILITY; PRESSURE RANGE MEGA PA 10-100; PYROCHLORE; RAMAN EFFECT; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; COHERENT SCATTERING; DIFFRACTION; ELECTRON MICROSCOPY; MICROSCOPY; MINERALS; PRESSURE RANGE; PRESSURE RANGE MEGA PA; SCATTERING; STABILITY

Citation Formats

Zhang, F.X., E-mail: zhangfx@umich.edu, Lang, M., Zhang, J.M., Ewing, R.C., E-mail: rodewing@umich.edu, and Nyman, M. Structural changes of (K,Gd){sub 2}Ta{sub 2}O{sub 7} pyrochlore at high pressure. United States: N. p., 2011. Web. doi:10.1016/j.jssc.2011.06.040.
Zhang, F.X., E-mail: zhangfx@umich.edu, Lang, M., Zhang, J.M., Ewing, R.C., E-mail: rodewing@umich.edu, & Nyman, M. Structural changes of (K,Gd){sub 2}Ta{sub 2}O{sub 7} pyrochlore at high pressure. United States. doi:10.1016/j.jssc.2011.06.040.
Zhang, F.X., E-mail: zhangfx@umich.edu, Lang, M., Zhang, J.M., Ewing, R.C., E-mail: rodewing@umich.edu, and Nyman, M. Thu . "Structural changes of (K,Gd){sub 2}Ta{sub 2}O{sub 7} pyrochlore at high pressure". United States. doi:10.1016/j.jssc.2011.06.040.
@article{osti_21580256,
title = {Structural changes of (K,Gd){sub 2}Ta{sub 2}O{sub 7} pyrochlore at high pressure},
author = {Zhang, F.X., E-mail: zhangfx@umich.edu and Lang, M. and Zhang, J.M. and Ewing, R.C., E-mail: rodewing@umich.edu and Nyman, M.},
abstractNote = {The structure of K-bearing tantalate pyrochlore (K{sub 2-x}Gd{sub x})Ta{sub 2}O{sub 6+x}(x{approx}0.4) was studied at high pressures using in situ X-ray diffraction and Raman scattering methods. Experimental results indicated that (K{sub 2-x}Gd{sub x})Ta{sub 2}O{sub 6+x}(x{approx}0.4) retains the pyrochlore structure up to 40 GPa, but partial amorphization occurred at pressures above 23 GPa. The amorphous phase was also confirmed in the quenched sample by means of transmission electron microscopy. The tantalate pyrochlore lattice is more stable than pyrochlore compounds in other systems, such as rare earth titanates, zirconates and stannates. The structural stability of pyrochlore tantalate may be mainly related to the size ratio of cations on the 16d and 16c sites in the lattice. - Graphical Abstract: In the pyrochlore tantalate, K and Gd co-occupy the 16d site and Ta is on the 16c site and forming octahedra with nearby anions. The pyrochlore tantalate is quite resistant to high pressure even when the structure is partially amorphized. Highlights: > In situ XRD measurements revealed that (KGd){sub 2}Ta{sub 2}O{sub 7} pyrochlore is much stable than other pyrochlore oxides at high pressures. > Pyrochlore tantalate can be partially amorphized at high pressures. > The enhanced phase stability of tantalate pyrochlore is due to the large size difference of cations.},
doi = {10.1016/j.jssc.2011.06.040},
journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = 9,
volume = 184,
place = {United States},
year = {2011},
month = {9}
}