Bi2La4O9: A Monoclinic Phase in the System Bi2O3–La2O3

• Published in: Journal of solid state chemistry 1996-07, Vol.124 (2), p.300-304
• Main Authors: Chen, X.L., Eysel, W., Li, J.Q.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Water, oxides, hydroxides, peroxides
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1996.0240

The binary system Bi2O3–La2O3with La2O3≥ 50 mole% has been investigated at 950–1000°C. The results revealed three compounds: Bi8La10O27, Bi2.4La3.6O9, and Bi2La4O9. Bi2.4La3.6O9has a rhombohedral subcell with hexagonal lattice parametersa= 3.96017(5) Å,c= 9.9691(2) Å, and space groupR3m. It is probably the same phase which was reported previously as Bi2La4O9(Refs. 5 and 6). Bi2La4O9has a monoclinic structure with the subcell lattice parametersa= 6.8290(3) Å,b= 3.9887(1) Å,c= 4.0524(1) Å and β = 125.094(3)° and subcell space groupC2/m. Its average structure has been determined by X-ray powder diffraction and refined by the Rietveld method. The average structure can be described as an oxygen deficient fluorite structure of the δ-Bi2O3type with La and Bi randomly distributed on the cation site. In addition, a superstructure has been observed by TEM.