Synthesis and Characterization of Ba2VO4 with the β-Ca2SiO4 Structure: Comparison with Sr2VO4

✍ Scribed by Guo Liu; J.E. Greedan

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 432 KB
• Volume: 103
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1095

✦ Synopsis

Phase-pure (\mathrm{Ba}{2} \mathrm{VO}{4}) has been synthesized by hydrogen reduction of a mixture of (\mathrm{Ba}{3} \mathrm{~V}{2} \mathrm{O}{8}) and (20 %) excess (\mathrm{BaCO}{3}) at (12000-1250^{\circ} \mathrm{C}), and its crystal structure, designited as (\beta-\mathrm{Ba}{2} \mathrm{VO}{4}), refined using a combination of powder neutron and X-ray diffraction data. It is monoclinic, space group (P 2_{1} / n) (no. 14). with (a=6.0191(7) \AA, b=7.6494(7), c=10.465(1), \beta=92.39(1)^{\circ}), and (V=481.4(2) \AA^{3}) from Guinier X-ray diffraction data. (\beta-\mathrm{Ba}{2} \mathrm{VO}{4}) is isostructural with (\beta-\mathrm{Ca}{2} \mathrm{SiO}{4}). The structure is closely related to (\beta-\mathrm{K}{2} \mathrm{SO}{4}) and consists of isolated (\mathrm{VO}{4}^{4-}) tetrahedra and loosely bonded (\mathrm{Ba}(\mathrm{I}) \mathrm{O}{10}) and (\mathrm{Ba}(2) \mathrm{O}{9}) polyhedra. Its magnetic behavior can be approximated as an (S=\frac{1}{2}) infinite Heisenberg linear chain. The crystal structure and magnetic properties of the (\beta-\mathrm{Ba}{2} \mathrm{VO}{4}) are compared with those of the structurally related high-temperature form of (\mathrm{Sr}{2} \mathrm{VO}{4}\left(\beta-\mathrm{Sr}{2} \mathrm{VO}{4}\right)). Reexamination of the crystal structure of the latter discloses that one of the V(IV) atons has a tare trigonal bipyramidal coordination and that this atom is weakly honded to a (\mathrm{VO} \mathrm{O}{4}) tetrathedron forming is (\mathrm{V}{2} \mathrm{O}{\mathrm{g}}^{\mathrm{K}}) - dimer. The formation mechanism of (\beta-\mathrm{Ba}{2} \mathrm{VO}{4}) and the possible existence of an orthorhombic form isostructural with (\beta-\mathrm{K}{3} \mathrm{SO}{4}) are also discussed. an 1993 Acalemic Press. Inc.