Structural and electrical properties of the 2Bi2O3·3ZrO2 system |
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Authors: | ?edomir Jovaleki? Dejan Poleti Miodrag Mitri? |
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Institution: | a Institute for Multidisciplinary Research, Kneza Višeslava 1, 11000 Belgrade, Serbia b Institute of Technical Sciences of the Serbian Academy of Sciences and Arts, Knez Mihailova 35, 11000 Belgrade, Serbia c Department of General and Inorganic Chemistry, Faculty of Technology and Metallurgy, Karnegijieva 4, 11000 Belgrade, Serbia d Laboratory of Crystallography, Faculty of Mining and Geology, ?ušina 7, 11000 Belgrade, Serbia e Laboratory of Solid State Physics, Institute for Nuclear Sciences “Vin?a”, P.O. Box 522, 11000 Belgrade, Serbia |
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Abstract: | Powder mixtures of α-Bi2O3 (bismite) and monoclinic m-ZrO2 (baddeleyite) in the molar ratio 2:3 were mechanochemically and thermally treated with the goal to examine the phases, which may appear during such procedures. The prepared samples were characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), electrical measurements, as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanochemical reaction leads to the gradual formation of a nanocrystalline phase, which resembles δ-Bi2O3, a high-temperature Bi2O3 polymorph. Isothermal sintering in air at a temperature of 820 °C for 24 h followed by quenching to room temperature yielded a mixture of ZrO2-stabilized β-Bi2O3 and m-ZrO2 phases, whereas in slowly cooled products, the complete separation of the initial α-Bi2O3 and m-ZrO2 constituents was observed. The dielectric permittivity of the sintered samples significantly depended on the temperature. The sintered and quenched samples exhibited a hysteresis dependence of the dielectric shift, showing that the ZrO2-doped β-Bi2O3 phase possess ferroelectric properties, which were detected for the first time. This fact, together with Rietveld refinement of the β-Bi2O3/m-ZrO2 mixture based on neutron powder diffraction data showed that ZrO2-doped β-Bi2O3 has a non-centrosymmetric structure with as the true space group. The ZrO2 content in the doped β-Bi2O3 and the crystal chemical reasons for the stabilization of the β-Bi2O3 phase by the addition of m-ZrO2 are discussed. |
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Keywords: | Ferroelectricity Mechanochemical treatment Bi2O3 ZrO2 |
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