Relations between Oxygen Deficiency and Structures in the La-Sr-Cu-O System. I. A New Oxygen-Deficient Phase, (La,Sr)5Cu5O13

✍ Scribed by Kenji Otzschi; Akihiko Hayashi; Yohko Fujiwara; Yutaka Ueda

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 257 KB
• Volume: 105
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1250

✦ Synopsis

A new compound in the (\mathrm{La}-\mathrm{Sr}-\mathrm{Cu}-\mathrm{O}) system was obtained by annealing (\mathrm{La}{5} \mathrm{SrCu}{6} \mathrm{O}{15}\left[\right.) or (\left(\mathrm{La}{0.8333} \mathrm{Sr}{0.1666}\right){8}) (\left.\mathrm{Cu}{8} \mathrm{O}{20}(8-8-20)\right]) at (600^{\circ} \mathrm{C}) under high (\mathrm{O}{2}) pressure ( (P{0_{2}}=300 \mathrm{~atm}) ). It crystallizes in a tetragonal cell with parameters (a \approx \sqrt{5} a_{\mathrm{p}}) and (c \approx a_{\mathrm{p}}), in the same way as (\mathrm{La}{4} \mathrm{BaCu}{5} \mathrm{O}{13+8}), where (a{\mathrm{p}}) means the cell constant of the cubic perovskite. By TG study the composition of this compound was estimated to be (\left(\mathrm{La}{0.8333} \mathrm{~S}{0.1666}\right){5} \mathrm{Cu}{5} \mathrm{O}{13.04 \pm 0.02}(5-5-13)). The structure has been refined in the space group (P 4 / m) by Rietveld analysis of powder X-ray diffraction. Lanthanum and strontium in the structure are statistically distributed, in contrast to (\mathrm{La}{4} \mathrm{BaCu}{5} \mathrm{O}{13+\delta}), where lanthanum and barium are located in an ordered manner. The oxygen nonstoichiometry and the electrical resistivity of (8-8-20) and (5-5-13) compounds are also discussed. (19) 1993 Academic Press, Inc.