Oxygen nonstoichiometry, Mossbauer spectra and mixed conductivity of Pr0.5Sr0.5O3-delta


The oxygen deficiency of perovskite-type Pr0.5Sr0.5FeO3-delta, studied by coulometric titration, thermogravimetry and Mossbauer spectroscopy, is significantly higher than that in La0.5Sr0.5FeO3-delta at 973-1223 K. The variations of hole mobility and Seebeck coefficient in oxidizing atmospheres, where the total conductivity of praseodymium-strontium ferrite is predominantly p-type electronic, suggest progressive delocalization of the p-type charge carriers on increasing oxygen chemical potential. As for other perovskite-type ferrites, reduction leads to the co-existence of vacancy-ordered and disordered domains. The n-type electronic conductivity of Pr0.5Sr0.5FeO3-delta at reduced P(O-2) and the hole transport under oxidizing conditions are both lower compared to the La-containing analogue. Analogous conclusion was drawn for the ionic conductivity, calculated from the steady-state oxygen permeation data under oxidizing conditions and from the P(O-2)-dependencies of total conductivity in the vicinity of electron-hole equilibrium points where the average iron oxidation state is 3+. The similar activation energies for partial ionic and electronic conductivities in Ln(0.5)Sr(0.5)FeO(3-delta) (Ln = La, Pr) indicate that the presence of praseodymium does not alter any of the conduction mechanisms but decreases the charge-carrier mobility due to the smaller radius of Pr3+ cations stabilized in the perovskite lattice. (c) 2006 Elsevier Ltd, All rights reserved.



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Chemistry; Physics


Kharton, VV; Patrakeev, MV; Waerenborgh, JC; Kovalevsky, AV; Pivak, YV; Gaczynski, P; Markov, AA; Yaremchenko, AA

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