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 00:00:00 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), Vol. 109:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

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