Local structure of the lead-free relaxor ferroelectric (K{sub x}Na{sub 1-x}){sub 0.5}Bi{sub 0.5}TiO{sub 3}

Journal Article · Sun May 01 04:00:00 EDT 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.71.174114· OSTI ID:20718992

Shuvaeva, V A; Zekria, D; Glazer, A M; Jiang, Q; Weber, S M; Bhattacharya, P; Thomas, P A ^[1]

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1. Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom)

The local environment of Bi and Ti atoms in the lead-free relaxor ferroelectric solid-solution (K{sub x}Na{sub 1-x}){sub 0.5}Bi{sub 0.5}TiO{sub 3} has been studied as a function of K concentration and as a function of temperature for the x=0 end member by x-ray absorption fine structure (XAFS). It is found that the local environment of Bi is much more distorted than that determined from conventional diffraction experiments. The shortest Bi-O distances are determined to be 2.22 A, and are 0.3 A shorter than those calculated from the crystallographic data. Several possible models of the Bi coordination environment, which are consistent with the XAFS data and provide bond-valence sums for Bi that are closer to the theoretical values, are proposed. The Ti displacement from the center of the oxygen octahedron increases with K concentration while the shortest Bi-O distance shows no compositional dependence. In K{sub 0.5}Bi{sub 0.5}TiO{sub 3} the value of the Ti displacement is determined to be 0.18 A. The changes of the macroscopic symmetry at the phase transition points in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} do not lead to changes of the radial atomic distribution around Ti, which is well off-center over the whole temperature range up to and including the paraelectric cubic phase. The results can be explained by assuming the presence of structural disorder.

• OSTI ID: 20718992
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 17 Vol. 71; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
ATOMS
BISMUTH COMPOUNDS
CRYSTAL STRUCTURE
DISTRIBUTION
FERROELECTRIC MATERIALS
FINE STRUCTURE
OXYGEN
PHASE TRANSFORMATIONS
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
SOLID SOLUTIONS
TEMPERATURE DEPENDENCE
TITANATES
VALENCE
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY