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Title: Structure and Thermal Expansion of YSZ and La 2Zr 2O 7 Above 1500°C from Neutron Diffraction on Levitated Samples

High-temperature time-of-flight neutron diffraction experiments were performed in this paper on cubic yttria-stabilized zirconia (YSZ, 10 mol% YO 1.5) and lanthanum zirconate (LZ) prepared by laser melting. Three spheroids of each composition were aerodynamically levitated and rotated in argon flow and heated with a CO 2 laser. Unit cell, positional and atomic displacement parameters were obtained by Rietveld analysis. Below ~1650°C the mean thermal expansion coefficient (TEC) for YSZ is higher than for LZ (13 ± 1 vs. 10.3 ± 0.6) × 10 -6/K. From ~1650°C to the onset of melting of LZ at ~2250°C, TEC for YSZ and LZ are similar and within (7 ± 2) × 10 -6/K. LZ retains the pyrochlore structure up to the melting temperature with Zr coordination becoming closer to perfectly octahedral. Congruently melting LZ is La deficient. The occurrence of thermal disordering of oxygen sublattice (Bredig transition) in defect fluorite structure was deduced from the rise in YSZ TEC to ~25 × 10 -6/K at 2350°C–2550°C with oxygen displacement parameters (U iso) reaching 0.1 Å 2, similar to behavior observed in UO 2. Acquisition of powder-like high-temperature neutron diffraction data from solid-levitated samples is feasible and possible improvements are outlined. Finally, this methodologymore » should be applicable to a wide range of materials for high-temperature applications.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3]
  1. Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab.
  2. Materials Development, Inc., Arlington Heights, IL (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
Publication Date:
Grant/Contract Number:
SC0001089; SC0004684; AC05-00OR22725; DESC0001089
Type:
Accepted Manuscript
Journal Name:
Journal of the American Ceramic Society
Additional Journal Information:
Journal Volume: 98; Journal Issue: 10; Journal ID: ISSN 0002-7820
Publisher:
American Ceramic Society
Research Org:
Univ. of California, Davis, CA (United States); Materials Development, Inc., Arlington Heights, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1361282
Alternate Identifier(s):
OSTI ID: 1400447