Coexistence of several sillenite-like phases in pseudo-binary and pseudo-ternary systems based on Bi2O3

A series of polycrystalline samples containing sillenite-like (doped gamma-Bi2O3) phases were prepared by high-temperature reactions from alpha-Bi2O3 powder and different oxides in six pseudo-binary Bi2O3-MxOy (M = Mn, Ti, V) and six pseudo-ternary Bi2O3-M1(x)O(y)-M2(x)O(y) (M1 = Pb, Zn, Ti and M2 = Zn, Ti, Si) systems. The products were characterized by XRD, SEM/EDX, HRTEM, SAED and DTA techniques. It is shown that for pseudo-binary systems, the phase composition of specimens depends on dopant content, while, for pseudo-ternary systems, depends on dopants radii, as well. In pseudo-binary systems, singlephase sillenites are obtained if the dopant content is in accordance with formula Bi12M4+O20, for M = Mn and Ti, and Bi-12(M-0.8(5+))O-20, for M = V. However, two coexisting sillenite-like phases, doped compound and nominally undoped solid solution, are found if a half of that dopant quantity is applied. In pseudoternary systems, the phase-pure double-doped sillenite specimens are identified if ionic radii of dopants differ less than 40%. Otherwise, two coexisting sillenites were obtained. The possibility to prepare the undoped gamma-Bi2O3 phase was also discussed. (C) 2013 Elsevier Masson SAS. All rights reserved.