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Title: A 2TiO 5 (A = Dy, Gd, Er, Yb) at High Pressure

Here, the structural evolution of lanthanide A 2TiO 5 (A = Dy, Gd, Yb, and Er) at high pressure is investigated using synchrotron X-ray diffraction. The effects of A-site cation size and of the initial structure are systematically examined by varying the composition of the isostructural lanthanide titanates, and the structure of dysprosium titanate polymorphs (orthorhombic, hexagonal and cubic), respectively. All samples undergo irreversible high pressure phase transformations, but with different onset pressures depending on the initial structure. While individual phase exhibits different phase transformation histories, all samples commonly experience a sluggish transformation to a defect cotunnite-like ( Pnma) phase for a certain pressure range. Orthorhombic Dy 2TiO 5 and Gd 2TiO 5 form P2 1am at pressures below 9 GPa and Pnma above 13 GPa. Pyrochlore-type Dy 2TiO 5 and Er 2TiO 5 as well as defect-fluorite-type Yb 2TiO 5 form Pnma at ~ 21 GPa, followed by Im3¯m. Hexagonal Dy 2TiO 5 forms Pnma directly, although a small amount of remnants of hexagonal Dy 2TiO 5 is observed even at the highest pressure (~ 55 GPa) reached, indicating a kinetic limitations in the hexagonal Dy 2TiO 5 phase transformations at high pressure. Decompression of these materials leads tomore » different metastable phases. Most interestingly, a high pressure cubic X-type phase ( Im3¯m) is confirmed using highresolution transmission electron microscopy on recovered pyrochlore-type Er 2TiO 5. The kinetic constraints on this metastable phase yield a mixture of both the X-type phase and amorphous domains upon pressure release. This is the first observation of an X-type phase for an A 2BO 5 composition at high pressure.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ; ORCiD logo [2] ;  [3] ; ORCiD logo [4] ;  [5] ;  [6] ; ORCiD logo [6] ;  [6] ;  [7] ;  [1]
  1. Stanford Univ., Stanford, CA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Carnegie Institution of Washington, Argonne, IL (United States)
  5. Univ. of Chicago, Chicago, IL (United States)
  6. Univ. of Tennessee, Knoxville, TN (United States)
  7. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 57; Journal Issue: 4; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1432057