Crystal Structure and Electrical Properties of the Pyrochlore Ruthenate Bi2-xYxRu2O7

✍ Scribed by R. Kanno; Y. Takeda; T. Yamamoto; Y. Kawamoto; O. Yamamoto

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 294 KB
• Volume: 102
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1012

✦ Synopsis

The bismuth yttrium pyrochlore ruthenates (\mathrm{Bi}{2-\gamma} \mathrm{Y}{8} \mathrm{Ru}{2} \mathrm{O}{7}) have been synthesized and characterized by (X)-ray Rietveld structure refinement and electrical conductivity measurement. Room temperature resistivities increase with (x), and a change from metallic to semiconducting behavior is observed between (x=1.2) and 1.4. The distortion of the (\mathrm{RuO}{6}) octahedra and the bend in the (\mathrm{RuO}{6}) zig-zag chains increase with (x). The transition from metallic to semiconducting state is correlated with the variation of the (\mathrm{R} u-\mathrm{O}-\mathrm{Ru}) angle from (139^{\circ}) at (x=0.0) to (129^{\circ}) at (x=2.0). The (\mathrm{Ru}-\mathrm{O}) bond length in the (\mathrm{RuO}_{6}) octahedra increases in the interval (0 \leq x \leq 1.2). This variation is understood to result from the contribution of (\mathbf{B i}) orbitals to the conduction band; in the metallic regime, (0 \leq x \leq 1,2), the electron transfer leads to short (\mathrm{Ru}-\mathrm{O}) bond length. whereas in the nonmetalic state there is little (\mathrm{Ru-O}) bond length variation because there is no contribution of the Bi electrons to the Ru (4 d) state. 1993 Academic Press. Inc.