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Time of flight neutron Rietveld refinement study at elevated temperature on a monoclinic near-stoichiometric NASICON

Journal Article · · J. Solid State Chem.; (United States)

Time of flight neutron powder data were collected at elevated temperatures on a sample of NASICON of composition Na/sub 3.17/Zr/sub 1.93/Si/sub 1.9/O/sub 12/. This sample, prepared by reheating a commercially available NASICON to minimize the ZrO/sub 2/ impurity, has been previously structurally refined from room temperature neutron diffraction data collected at Argonne National Laboratory. Conductivity measurements show a cusp at ca. 170/sup 0/C attributed to the monoclinic-rhombohedral transition and the purpose of this work was to explore the nature of the transition. Data runs were made at 143, 173, 202, 300, and 391/sup 0/C. No evidence for a crystal system change was found. The highest temperature data sets could not be refined satisfactorily by the Rietveld method using a rhombohedral model, but rather required a monoclinic cell in space group C2/c to achieve convergence. An explanation for the conductivity cusp is given in terms of disordering of the sodium ions and a change in conduction pathways which lowers the barriers to ion movement.

Research Organization:
Texas A and M Univ., College Station (USA)
DOE Contract Number:
W-31109-ENG-38
OSTI ID:
7078694
Journal Information:
J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 72:1; ISSN JSSCB
Country of Publication:
United States
Language:
English