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Oxygen nonstoichiometry, Mössbauer spectra and mixed conductivity of Pr0.5Sr0.5FeO3−δ

2007; Elsevier BV; Volume: 68; Issue: 3 Linguagem: Inglês

10.1016/j.jpcs.2006.11.023

1879-2553

В.В. Хартон, М.В. Патракеев, João C. Waerenborgh, Andrei V. Kovalevsky, Yevheniy Pivak, P. Gaczyński, A.A. Markov, Aleksey A. Yaremchenko,

Electronic and Structural Properties of Oxides

The oxygen deficiency of perovskite-type Pr0.5Sr0.5FeO3−δ, studied by coulometric titration, thermogravimetry and Mössbauer spectroscopy, is significantly higher than that in La0.5Sr0.5FeO3−δ 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−δ at reduced p(O2) 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(O2)-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 Ln0.5Sr0.5FeO3−δ (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.