Displacive disorder in three high-k bismuth oxide pyrochlores

Journal Article · Thu May 25 04:00:00 EDT 2006 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2006.02.004· OSTI ID:20895215

Melot, B ^[1]; Rodriguez, E ^[1]; Proffen, Th ^[2]; Hayward, M A ^[3]; Seshadri, R ^[1]

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1. Materials Department and Materials Research Laboratory, University of California, Santa Barbara, CA 93106 (United States)
2. Los Alamos National Laboratory, Manuel Lujan Jr. Neutron Scattering Center LANSCE-12, MS H805, Los Alamos, NM 87545 (United States)
3. Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR (United Kingdom)

We use time-of-flight neutron powder diffraction to examine static displacive disorder in three different pyrochlore A{sub 2}B{sub 2}O{sub 6}O' compounds with Bi on the A site. The compounds (Bi{sub 1.5}Zn{sub 0.5})(Nb{sub 1.5}Zn{sub 0.5})O{sub 6}O' (BZN) (Bi{sub 1.5}Zn{sub 0.5})(Ta{sub 1.5}Zn{sub 0.5})O{sub 6}O' (BZT), and (Bi{sub 1.5}Zn{sub 0.5})(Sb{sub 1.5}Zn{sub 0.5})O{sub 6}O' (BZS), are of interest - particularly BZN - for their high dielectric constants in the absence of any phase transition from the cubic high temperature phase. The local structures of the three compounds is characterized by displacive disorder from the ideal pyrochlore positions for both the A and O' sites, with the precise nature of the disorder being quite similar. However the extent of displacive disorder is different, despite the B-O networks being nearly identical in the three compounds. The reported dielectric constants of the three compounds are related to the extent of local displacement, and BZN, with the largest extent of local atomic displacement of A and O', is also reported to have the largest dielectric constant at 1 MHz. The dielectric constants are also related to the magnitudes of the thermal parameters of the different ions. The strongest correlation is found to involve the thermal parameter on the B site (Nb, Ta, or Sb)

• OSTI ID: 20895215
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 5 Vol. 41; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMIC DISPLACEMENTS
BISMUTH OXIDES
MHZ RANGE 01-100
NEUTRON DIFFRACTION
PERMITTIVITY
PHASE TRANSFORMATIONS
PYROCHLORE
TIME-OF-FLIGHT METHOD