Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1296447 | Solid State Ionics | 2011 | 7 Pages |
Abstract
Low-temperature ordering transitions in polycrystalline high temperature conductors (Dy1 â xCax)2Ti2O7 â δ (x = 0, 0.1) prepared using co-precipitation, mechanical activation and solid-state reactions at 1400 or 1600 °C have been studied by impedance spectroscopy at low frequencies and thermal mechanical analysis (TMA). The dielectric permittivity and loss tangent of the ceramics obtained have been measured as a function of temperature at low frequencies (0.5â500 Hz). The results provide evidence for the relaxation of point defects, most likely oxygen vacancies, at 500â600 °C and an antiferroelectric low-temperature phase transition of the second order, associated with re-arrangement process in the oxygen sublattice of pyrochlore structure. The temperature of the antiferroelectric transition is 700 to 800 °C, depending on the synthesis procedure and ceramic composition. Calcium doping of Dy2Ti2O7 leads to the formation of additional oxygen vacancies and, in the case of the samples prepared via co-precipitation, increases the peaks in permittivity due to the relaxation process and ordering transition by three or six times, respectively.
Keywords
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Physical Sciences and Engineering
Chemistry
Electrochemistry
Authors
D.A. Belov, A.V. Shlyakhtina, S.Yu. Stefanovich, A.N. Shchegolikhin, A.V. Knotko, O.K. Karyagina, L.G. Shcherbakova,