Structure and ionic conductivity of Bi6Cr2O15, a new structure type containing (Bi12O14)(n)(8n+) columns and CrO42- tetrahedra

摘要

Powder samples of the Cr6+-containing compound Bi6Cr2O15 were prepared by solid state reaction of Bi2O3 and Cr2O3 in air at 650degreesC. The structure was solved and refined using high-resolution neutron powder diffraction data in space group Ccc2, with anisotropic thermal displacement parameters a = 12.30184(5), h = 19.87492(7), and c = 5.88162(2) Angstrom, V= 1438.0 Angstrom(3), and 126 variables to R-F = 1.8%. Bi6Cr2O15 exhibits a new structure type that contains (Bi12O14)(n)(8n+) columns, of the kind previously found only for phases isotypic with Bi13MO4VO34. Each column is surrounded by eight CrO42- tetrahedra. The ionic conductivity of Bi6Cr2O15 was determined by impedance measurements to be 3.5 X 10(-5) (Omega cm)(-1) at 600degreesC. 2002 Elsevier Science. [References: 28]