Synthesis, structure and properties of doped Bi2O3

Oxide ion conductors have been increasingly studied for many years because of their application in devices with high economical interest such as solid oxide fuel cells (SOFC), oxygen sensors, dense ceramic membranes for oxygen separation, and membrane reactors for oxidative catalysis. Bismuth oxides present polymorph forms, such as delta-, beta- or gamma-Bi2O3, with great potential for such applications, alone or in combination with other oxides. The present study investigates the influence of selected ions (Fe3+, Sb3+/Sb5+, and Ta5+), introduced as dopant in alpha-Bi2O3 and their effect on the structure and properties of the oxide polymorph forms obtained, at high temperature. The molar ratio was Bi2O3:MxOy 0.95:0.05 where M = Fe2O3, Sb2O3 or Ta2O5, respectively. The structural changes of alpha-Bi2O3 were analysed by powder X-ray diffraction, SEM/EDX analysis and infrared spectroscopy. The structural changes are correlated with bulk ceramic characteristics (density, porosity) and their electrical behaviour versus temperature. The presence of some dopants (antimony and tantalum) on bismuth sites enlarges and enhances the stability of the polymorph forms, which is relevant to potential application. (c) 2006 Elsevier Ltd. All rights reserved.