期刊
JOURNAL OF APPLIED PHYSICS
卷 121, 期 4, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.4974871
关键词
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资金
- Materials Science of Actinides, an Energy Frontier Research Center - U.S. Department of Energy (DOE) Office of Science, Basic Energy Sciences [DE-SC0001089]
- DOE-NNSA [DE-NA0001974]
- DOE-BES [DE-FG02-99ER45775]
- NSF
- DOE Office of Science by ANL [DE-AC02-06CH11357]
- Office of Science, Office of Basic Energy Sciences, of the U.S. DOE [DE-AC02-05CH11231]
- McGee Research Grant program through Stanford University
In situ high-pressure X-ray diffraction and Raman spectroscopy were used to determine the influence of composition on the high-pressure behavior of A(2)B(2)O(7) pyrochlore (A = Eu, Dy; B = Ti, Zr) up to similar to 50 GPa. Based on X-ray diffraction results, all compositions transformed to the high-pressure cotunnite structure. The B-site cation species had a larger effect on the transition pressure than the A-site cation species, with the onset of the phase transformation occurring at similar to 41 GPa for B = Ti and similar to 16 GPa B = Zr. However, the A-site cation affected the kinetics of the phase transformation, with the transformation for compositions with the smaller ionic radii, i.e., A = Dy, proceeding faster than those with a larger ionic radii, i.e., A = Eu. These results were consistent with previous work in which the radius-ratio of the A-and B-site cations determined the energetics of disordering, and compositions with more similarly sized A-and B-site cations had a lower defect formation energy. Raman spectra revealed differences in the degree of short-range order of the different compositions. Due to the large phase fraction of cotunnite at high pressure for B = Zr compositions, Raman modes for cotunnite could be observed, with more modes recorded for A = Eu than A = Dy. These additional modes are attributed to increased short-to-medium range ordering in the initially pyrochlore structured Eu2Zr2O7 as compared with the initially defect-fluorite structured Dy2Zr2O7. Published by AIP Publishing.
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