Crystal Structure of La24Li20Ti5O56: A Pseudo-Close-Packed, Columnar Intergrowth Stucture

✍ Scribed by Caroline A. Kirk; Anthony R. West

• Book ID: 102974992
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 878 KB
• Volume: 162
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9328

✦ Synopsis

The crystal structure of La 24 Li 20 Ti 5 O 56 has been solved by a combination of selected area electron di4raction (SAED) and powder X-ray and neutron di4raction. The structure has a strong tetragonal subcell a ‫؍‬ 13.244(1) A s , c ‫؍‬ 7.463(1) A > , space group P4/mbm (127); by SAED, a weak supercell with doubled c is observed. The subcell structure contains alternating columns of (i) perovskite-like structure, with Li, Ti in alternating octahedral sites, and (ii) a more complex structure that is distantly related to 6uorite; one half of the tetrahedral sites in 6uorite is occupied in pairs by Li, but the other half of the pairs of tetrahedral sites collapse to contain either a single octahedral site occupied by Ti, or a single tetrahedral site occupied by Li. The Li sites that form the edge-sharing pairs are not fully occupied. Possible ordering of Li/vacancies within these sites may be responsible for the superstructures seen by SAED. The structure is not close-packed, cp, overall but the cp arrangements of O and La within the columns give the structure a high packing density.