Electrical Properties of a CeO₂-Bi2O3Mix System Elaborated at 600°C

Abstract

The electrical conduction of a series of polycristalline [(1−x)CeO2⋅x/2Bi2O3] samples has been analyzed using electrical impedance spectroscopy, in the temperature range 25 to750∘C. Samples have been prepared via a coprecipitation route followed by a pyrolysis process at600∘C. For compositionsx≤0.20, Ce1−xBixO2−x/2solid solutions, with fluorite cubic structure, are obtained. In the composition range0.30≤x≤1, the system is biphasic with coexistence of cubic and tetragonal structures. To interpret the Nyquist representations of electrical analyses, various impedance models including constant phase elements and Warburg impedances have been used. In the biphasic range (0.30≤x≤0.7), the conductivity variation might be related to the increasing fraction of two tetragonal β′and β-Bi2O3phases. The stabilization of the tetragonal phase coexisting with substituted ceria close to compositionx=0.7is associated with a high conduction of the mix system CeO2-Bi2O3.

Multifunctional rare earth or bismuth oxide materials for catalytic or electrical applications

“…The polycrystalline RE oxides (CeO 2 , La 2 O 3 , Lu 2 O 3 ) have been subjected to air-CH 4 or air-CO gas flows (2500 ppm CH 4 or CO in air). The CO 2 gas resulting from catalytic oxidation was analyzed using Fourier Transform infrared (FTIR) spectroscopy of emitted gases.…”

“…The catalytic interactions between this system and air-CH 4 or air-CO flows are discussed. Low catalytic activity has been observed in the case of CH 4 interacting with the mix system, while strong activity is observed in the case of CO interacting with bismuth rich system.…”

“…Low catalytic activity has been observed in the case of CH 4 interacting with the mix system, while strong activity is observed in the case of CO interacting with bismuth rich system. Figures 3 and 4 show the time dependent evolutions of vibrational band intensities I(t,T) of CO 2 gas formed from CO or CH 4 oxidations after a long oxidation period.…”

“…The observed intensities I(t,T) obs of CO 2 vibrational bands resulting from oxidations of CH 4 or CO have been interpreted through a unique time dependent model derived from the Avrami model, and describing the solid gas interaction mechanisms.…”

“…In the case of RE oxide [1,2] and CeO 2 -Bi 2 O 3 materials [3,4], infrared spectroscopy as a function of time (t) and temperature (T) has been used to determine the catalytic oxidation rates of CH 4 or CO into CO 2 . In the case of bismuth based system [(1 − x)CeO 2 − (x/2)Bi 2 O 3 ] with 0 < x < 1, electrical impedance spectroscopy (EIS) has been used to determine the conductivities as a function of bismuth fraction (x) and temperature (T).…”