Displacive disorder and dielectric relaxation in the stoichiometric bismuth-containing pyrochlores, Bi{sub 2}M{sup III}NbO{sub 7} (M=In and Sc)

Journal Article · Thu Oct 15 04:00:00 EDT 2009 · Journal of Solid State Chemistry

OSTI ID:21372341

Yun, Liu ^[1]; Nguyen, Hai Binh; Elliott, Kim ^[1]; Qijun, Ren; Zhanghai, Chen ^[2]

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1. Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)
2. Surface Physics Laboratory and Physics Department, Fudan University, Shanghai 200433 (China)

The structural disorder and temperature-dependent dielectric properties of two Bi-based niobate pyrochlore systems which have both previously been reported to occur at the ideal Bi{sub 2}(M{sup III}Nb{sup V})O{sub 7} stoichiometry without any compositional disorder on the pyrochlore A site, namely the Bi{sub 2}InNbO{sub 7} (BIN) and Bi{sub 2}ScNbO{sub 7} (BSN) pyrochlore systems, have been carefully re-investigated. It is established that A site stoichiometric, Bi-based niobate pyrochlores can indeed exist. Electron diffraction is used to investigate the nature of the displacive disorder therein both at room temperature as well as at close to liquid nitrogen temperature. The characteristic structured diffuse scattering observed arises from beta-cristobalite-like, 1-d correlated rotations and associated translations of chains of corner-connected O'Bi{sub 4} tetrahedra. The temperature-dependent dielectric properties including the low temperature dielectric relaxation properties of these A site stoichiometric, Bi-based niobate pyrochlores are also reported as are the micro-Raman spectra thereof. The experimental results suggest that the dipoles as well as the glassy relaxation behaviour in these Bi-based pyrochlores are directly related to these beta-cristobalite-like, correlated rotations of <110> chains of corner-connected O'Bi{sub 4} tetrahedra. - Graphical abstract: The characteristic 1-d, beta-cristobalite type displacive disorder of the O'Bi{sub 2} tetrahedral sub-structure responsible for the dipoles and glassy relaxation behaviour of the BIN and BSN, Bi-pyrochlores.

• OSTI ID: 21372341
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 10 Vol. 182; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
BISMUTH COMPOUNDS
COHERENT SCATTERING
CRISTOBALITE
DIELECTRIC MATERIALS
DIELECTRIC PROPERTIES
DIFFRACTION
DIFFUSE SCATTERING
DIPOLES
ELECTRICAL PROPERTIES
ELECTRON DIFFRACTION
MATERIALS
MINERALS
MULTIPOLES
NIOBATES
NIOBIUM COMPOUNDS
OXIDE MINERALS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PYROCHLORE
RAMAN SPECTRA
REFRACTORY METAL COMPOUNDS
SCATTERING
SILICATE MINERALS
SPECTRA
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TRANSITION ELEMENT COMPOUNDS