Crystal structure and metal-semiconductor transition of the Bi[sub 2[minus]x]Ln[sub x]Ru[sub 2]O[sub 7] pyrochlores (Ln = Pr-Lu)

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1994.1116· OSTI ID:7181952

Yamamoto, T ^[1]; Kanno, R; Kawamoto, Y ^[2]; Takeda, Y; Yamamoto, O ^[3]; Takano, M ^[4]

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1. Mie Univ., Tsu, Mie-ken (Japan) Central Research Institute of Electric Power Industry, Yokosuka (Japan)
2. Kobe Univ., Kobe, Hyogo-ken (Japan)
3. Mie Univ., Tsu, Mie-ken (Japan)
4. Kyoto Univ., Uji, Kyoto-fu (Japan)

The quaternary pyrochlore ruthenates, Bi[sub 2[minus]z]Ln[sub x]Ru[sub 2]O[sub 7] (Ln = Pr-Lu), have been synthesized and characterized by X-ray Rietveld structure refinement and electrical conductivity measurements. Room temperature resistivities increase with x, and a change from metallic to semiconducting behavior is observed between x = 1.2 and 1.4. In this composition region, smooth change from metallic to semiconducting behavior was observed at 40-80 K for the Pr-Sm systems, whereas no change was observed for the Dy and Y systems. Lattice parameters increase with x in the systems with larger rare earth cations (Pr, Nd), and decrease with x in the systems with smaller rare earth cations (Sm, Dy). However, the room-temperature structure analysis indicated similar structural changes in these solid solutions; the Ru-O bond length in the RuO[sub 6] octahedra increases, the distortion of the RuO[sub 6] octahedra increases, and the bend in the RuO[sub 6] octahedra increases, and the bend in the RuO[sub 6] zig-zag chains increases with increasing Ln contents. This corresponds to the change from metallic to semiconducting behavior around x = 1.2-1.4. The RuO[sub 6] octahedra distortion and the bend in the RuO[sub 6] zig-zag chains increase in the order Lu to Pr. the semiconductor-metal transition is discussed from the structural change.

• OSTI ID: 7181952
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 109:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
BISMUTH COMPOUNDS
BISMUTH OXIDES
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
LATTICE PARAMETERS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
RUTHENIUM COMPOUNDS
RUTHENIUM OXIDES
SCATTERING
SOLID SOLUTIONS
SOLUTIONS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION