Oxygen nonstoichiometry, Mössbauer spectra and mixed conductivity of Pr0.5Sr0.5FeO3−δ |
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Authors: | VV Kharton MV Patrakeev AV Kovalevsky P Gaczyński AA Yaremchenko |
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Institution: | a Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal b Institute of Physicochemical Problems, Belarus State University, 14 Leningradskaya Str., 220050 Minsk, Belarus c Institute of Solid State Chemistry, Ural Division of RAS, 91 Pervomaiskaya Str., Ekaterinburg 620219, Russian Federation d Chemistry Department, ITN/CFMC-UL, Estrada Nacional 10, P-2686-953 Sacavém, Portugal |
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Abstract: | 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. |
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Keywords: | A Oxides C Mö ssbauer spectroscopy D Defects D Diffusion D Electrical properties |
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