Calcium Insertion in the Na4Mn9O18 Tunnel Structure: Na1.1Ca1.8Mn9O18

✍ Scribed by N. Floros; C. Michel; M. Hervieu; B. Raveau

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 541 KB
• Volume: 162
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9338

✦ Synopsis

A new mixed valent manganese oxide, Na 1.1 Ca 1.8 Mn 9 O 18 , with a tunnel structure closely related to that of Na 4 Mn 9 O 18 has been synthesized. It crystallizes in the Pnma space group with a ‫؍‬ 26.418(2) A s , b ‫؍‬ 5.6468(4) A s , and c ‫؍‬ 9.1384(8) A s . Its structural study, combining X-ray powder di4raction and electron microscopy, shows that the [Mn 9 O 18 ] framework is similar to that of Na 4 Mn 9 O 18 , forming large S-shaped and six-sided tunnels running along b. In contrast, the positions and distributions of calcium in the tunnels are di4erent from those obtained for sodium in Na 4 Mn 9 O 18 , explaining the doubling of the periodicity along the tunnel axis direction. The insulating properties of these oxides agree with a tendency to ordering of the Mn 3؉ and Mn 4؉ species in di4erent sites.