Hydrothermal Synthesis of Lanthanum Vanadates: Synthesis and Crystal Structures of Zircon-Type LaVO4 and a New Compound LaV3O9

✍ Scribed by Yoshio Oka; Takeshi Yao; Naoichi Yamamoto

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 316 KB
• Volume: 152
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8717

✦ Synopsis

In the course of hydrothermal synthesis of lanthanum vanadates, zircon-type LaVO 4 and LaV 3 O 9 have been obtained and structurally characterized. The former is a metastable phase, and the latter is a new compound. Single-crystal X-ray di4ractometry con5rmed the zircon-type structure for LaVO 4 : I4 1 /amd with a ‫؍‬ 7.4578(7) A s , c ‫؍‬ 6.5417(9) A s , and Z ‫؍‬ 4; R ‫؍‬ 0.020 and R w ‫؍‬ 0.025 for 276 re6ections with I > 3 (I). The structure consists of isolated VO 4 tetrahedra which surround the La atom to form a LaO 8 dodecahedron. LaV 3 O 9 adopts the monoclinic system: P2 1 /m with a ‫؍‬ 4.949(2) A s , b ‫؍‬ 9.547(3) A s , c ‫؍‬ 7.411(2) A s , ‫؍‬ 100.76(2)3, and Z ‫؍‬ 2; R ‫؍‬ 0.035 and R w ‫؍‬ 0.042 for 1868 re6ections with I > 3 (I). The structure adopts a chaintype one consisting of a V 3 O 9 chain along [010] which is made up of edge-sharing VO 5 trigonal-bipyramid pairs and VO 4 tetrahedra. The La atom residues between the V 3 O 9 chains and is coordinated with ten oxygens. The present study demonstrates the applicability of hydrothermal method to the synthesis of new and/or metastable lanthanide vanadates.