Structural Properties of Nonstoichiometric Barium and Strontium Peroxides: BaO2−x (1.97≥2−x≥1.72) and SrO2−x (1.98≥2−x≥1.90)

✍ Scribed by Markus Königstein

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 153 KB
• Volume: 147
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8402

✦ Synopsis

The crystal structures of eight single crystals of barium and strontium peroxide, prepared by high pressure}high temperature synthesis, were determined by X-ray di4raction. The crystallographic data were successfully re5ned in the calcium carbide structure (space group I4/mmm, Z‫.)2؍‬ The results clearly indicate that the peroxides are nonstoichiometric compounds, MO 2؊x (M‫؍‬Ba, Sr), with a peroxide de5ciency and that oxide ions are present on interstitial lattice sites. The composition rage extends from near stoichiometry to compounds with a total oxygen content of 1.72 in the barium and 1.90 in the strontium peroxide. We 5nd that the oxide ions, replacing the peroxide molecular ions, occupy an interstitial position that is in the middle of the replaced peroxide molecular ion. A decrease of the peroxide content in the crystals results in a decreased c-axis of the tetragonal unit cell of the structure, while the a-axis is almost constant. Furthermore, the peroxide bond length decreases, as was con5rmed by Raman spectroscopy.

1999 Academic Press

The quotation marks are used to indicate that the compound is nonstoichiometric.