Determination of the Oxidation States of Cu and Ru in the System La2−xSrxCu1−yRuyO4−δ by XANES-Measurements

✍ Scribed by Stefan Ebbinghaus; Zhiwei Hu; Armin Reller

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 246 KB
• Volume: 156
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8981

✦ Synopsis

Numerous samples of the system La 2؊x Sr x Cu 1؊y Ru y O 4؊ (0.86 4 x 4 2, 0.05 4 y 4 1) as well as several other cuprates and ruthenates have been investigated by XANES spectroscopy. The exact energy positions of the white lines observed at the Cu+ and Ru+L III absorption edges are a sensitive measure for the oxidation state of the corresponding transition metal. Our results lead to the following fundamental conclusions: (i) Charge compensation in the system La 2؊x Sr x Cu 1؊y Ru y O 4؊ is achieved by a successive oxidation of Ru 4؉ to Ru 5؉ , while copper remains in the oxidation state 2؉. (ii) The formation of Ru 6؉ ions or higher oxidized species can be ruled out. (iii) For those compounds in which charge neutrality is not possible by the formation of Ru 5؉ alone, the remaining electron 99holes:: are located at the oxygen sites. The possibility of using the valence shift as a quantitative measure for the oxidation state of Ru in new compounds is brie6y discussed.