Transport properties and structural stability of tetragonal CeNbO4+δ |
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| Institution: | 1. Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal;2. Department of Materials, Imperial College London, Prince Consort Road, London, SW7 2BP, UK;3. Institute of Physicochemical Problems, Belarus State University, 14 Leningradskaya Str., 220050 Minsk, Belarus;1. Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 12500, India;2. Department of Physics, Maharishi Dayanand University, Rohtak 124001, India;3. Department of Physics and Astrophysics, University of Delhi, Delhi 11000, India;4. Department of Physics, Indira Gandhi University Meerpur, 123401 Rewari, India;1. High Pressure and Synchrotron Radiation Physics Division, Mumbai, India;2. Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India;1. Center for Fuel Cell Innovation, School of Materials Science and Engineering, State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science & Technology, Wuhan, Hubei 430074, China;2. Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang, Sichuan, China |
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| Abstract: | The electrical properties of CeNbO4+δ have been investigated at 1073–1223 K in the oxygen partial pressure range 10− 17 to 0.36 atm. The conductivity and Seebeck coefficient behaviour indicates that, at oxygen chemical potentials close to atmospheric, tetragonal CeNbO4+δ possesses a mixed ionic and p-type electronic conductivity. The ion transference numbers under the p(O2) gradient of 0.93/0.21 atm, measured by the modified e.m.f. technique, are close to 0.4 decreasing in more reducing environments. The variations of partial ionic and electronic conductivities can be described in terms of the oxygen intercalation into the scheelite-type lattice, which results in increasing concentrations of both dominant charge carriers, oxygen interstitials and holes, when p(O2) increases. Reduction leads to p(O2)-independent electrical properties, followed by a drastic decrease in the conductivity at oxygen pressures below 10− 15–10− 9 atm due to a reversible transition into the monoclinic phase. Contrary to the zircon-type CeVO4±δ, no traces of the parent binary oxides were detected in the reduced cerium niobate. |
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