Relations between Oxygen Deficiency and Structures in the La-Sr-Cu-O System: II. A New Oxygen-Deficient Phase (La, Sr)4Cu4O10

✍ Scribed by Kenji Otzschi; Yutaka Ueda

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 375 KB
• Volume: 107
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1332

✦ Synopsis

We report the synthesis and the structural properties of a new oxygen-deficient perovskite with the formula (\left.\left(\mathrm{La}{1-x} \mathrm{Sr}{x}\right){4} \mathrm{Cu}{4} \mathrm{O}{10}(x=0.1429)(\mathrm{Sr} / \mathrm{La}=1 / 6): 4-4-10\right)). It crystallizes in an orthorhombic cell with the parameters (a \approx 2 \sqrt{2} a{\mathrm{p}}, b \approx \sqrt{2} a_{\mathrm{p}}), and (c \approx a_{\mathrm{p}}), where (a_{\mathrm{p}}) means the cell constant of an ideal cubic perovskite. According to the crystal structure which has been refined in the space group Pbam by Rietveld analysis of powder X-ray diffraction (XRD), it has the same structure as (\mathrm{CaMnO}{2.5}), and lanthanum and strontium ions in the structure are statistically distributed as well as the other compounds, (\left(\mathrm{La}{1-x} \mathrm{Sr}{x}\right){8} \mathrm{Cu}{8} \mathrm{O}{20}(0.16 \leq x \leq 0.24: 8-8-20)) and (\left(\mathrm{La}{1-x} \mathrm{Sr}{x}\right){5} \mathrm{Cu}{5} \mathrm{O}{13}(x=0.1666(\mathrm{Sr} / \mathrm{La}=) 1/5) : 5-5 13). This newly found 4-4-10 compound, however, is constituted by only one type of (\mathrm{Cu}-\mathrm{O}) polyhedron, i.e., (\mathrm{CuO}{5}) pyramids, while the (8-8-20) and the (5-5-13) compounds include (\mathrm{CuO}{6}) octahedra and/or (\mathrm{CuO}{4}) squares in the structure as well. TG-DTA study and XRD measurement at high temperature revealed the structural phase transition of 4-4-10 to (8-8-20) around (550^{\circ} \mathrm{C}) without any gain or loss of oxygen. Some physical properties are also reported. C1993 Academic Press, Inc.