Partial charge ordering in the mixed-valent compound

✍ Scribed by H. Mizoguchi; W.J. Marshall; A.P. Ramirez; A.W. Sleight; M.A. Subramanian

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 459 KB
• Volume: 180
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2007.09.031

✦ Synopsis

Crystals of the mixed-valent compound Bi 6 O 5 ð ÞRh 3þ 8 Rh 4þ 4 O 24 were grown from a flux. The room temperature conductivity of a crystal was 3 S/cm but decreased smoothly with decreasing temperature to 10 À5 S/cm at 25 K. Magnetic susceptibility data indicate a localized moment for Rh 4+ . A Seebeck coefficient at 200 K of +280 mV/K further confirms that this compound is a semiconductor rather than a metal with a partially filled 4d t 2g band. A structure refinement based on single crystal X-ray diffraction data obtained at 173 and 296 K provided Rh-O distances sufficiently accurate to indicate the nature of the charge ordering between Rh 3+ and Rh 4+ . The large Seebeck coefficient coupled with the high electrical conductivity indicates that this may be a promising low-temperature thermoelectric material.