Order-disorder phase transitions and high-temperature oxide ion conductivity of Er2+xTi2−xO7−δ (x = 0, 0.096) |
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Authors: | AV Shlyakhtina AV Levchenko VYu Bychkov VA Rassulov OK Karyagina |
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Affiliation: | a Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow 119991, Russia b Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432, Russia c UIDM, ESTG, Instituto Politecnico de Viana do Castelo, Apartado 574, 4901-908 Viana do Castelo, Portugal d All-Russia Research Institute of Mineral Resources, Staromonetnyi per. 31, Moscow 119017, Russia e Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow 119991, Russia |
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Abstract: | The Er2+xTi2−xO7−δ (x = 0.096; 35.5 mol% Er2O3) solid solution and the stoichiometric pyrochlore-structured compound Er2Ti2O7 (x = 0; 33.3 mol% Er2O3) are characterized by X-ray diffraction (phase analysis and Rietveld method), thermal analysis and optical spectroscopy. Both oxides were synthesized by thermal sintering of co-precipitated powders. The synthesis study was performed in the temperature range 650-1690 °C. The amorphous phase exists below 700 °C. The crystallization of the ordered pyrochlore phase (P) in the range 800-1000 °C is accompanied by oxygen release. The ordered pyrochlore phase (P) exists in the range 1000−1200 °C. Heat-treatment at T ≥ 1600 °C leads to the formation of an oxide ion-conducting phase with a distorted pyrochlore structure (P2) and an ionic conductivity of about 10−3 S/cm at 740 °C. Complex impedance spectra are used to separately assess the bulk and grain-boundary conductivity of the samples. At 700 °C and oxygen pressures above 10−10 Pa, the Er2+xTi2−xO7−δ (x = 0, 0.096) samples are purely ionic conductors. |
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Keywords: | A Ceramics A Oxides B Chemical synthesis C Electrochemical measurements C Impedance spectroscopy |
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