Influence of magnesium on dielectric properties of Ca9–xMgxBi(VO4)7 ceramics

Dorbakov, N.G.; Grebenev, V.V.; Titkov, V.V.; Zhukovskaya, E.S.; Stefanovich, S.Y.; Baryshnikova, O.V.; Deyneko, D.V.; Morozov, V.A.; Belik, A.A.; Lazoryak, B.I.

Авторы: Dorbakov Nikolai G., Grebenev Vadim V., Titkov Vladimir V., Zhukovskaya Evgeniya S., Stefanovich Sergey Y., Baryshnikova Oksana V., Deyneko Dina V., Morozov Vladimir A., Belik Alexei A., Lazoryak Bogdan I.
Журнал: Journal of the American Ceramic Society
Том: 101
Номер: 9
Год издания: 2018
Издательство: American Ceramic Society
Местоположение издательства: United States
Первая страница: 4011
Последняя страница: 4022
DOI: 10.1111/jace.15545
Аннотация: Solid solution compositions of Ca9‐xMgxBi(VO4)7 in powder and ceramic forms are obtained by solid‐state reactions. Details of their crystal structures are determined for x = 0.25 and x = 0.5 powders by synchrotron radiation diffraction and the Rietveld method. The refinement has confirmed that Mg²⁺ is replacing Ca²⁺ in M5 position of polar (S.G. R3c) β‐Ca3(PO4)2‐type structure. Thermal analysis, dielectric and second harmonic generation experiments in broad temperature region have proved this polar structure to be stable in between 0 ≤ x ≤ 0.7. Magnesium for calcium substitution enlarges optical nonlinear activity of Ca9‐xMgxBi(VO4)7 in 0 < x ≤ 0.5. Two phase transitions have been found, one of which from polar to centrosymmetric phase is accompanied by dielectric constant peak of ferroelectric type. The other is upper on temperature, marked with smaller dielectric anomaly, and goes between two centrosymmetric phases. Temperatures of the phase transition only slightly depend on x, the first being near 1050 K, the second near 1100 K. Electric conductivity quickly rises with temperature in the polar phase. At higher temperature it changes according to the Arrhenius law with small activation energy, Ea ~0.7 eV for bulk conductivity and Egb ~2.0 ‐ 2.5 eV for grain boundary conductivity. The analysis of bulk and grain boundary conductivities agrees with Ca²⁺‐ion fast transport in ceramics. The bulk conductivity slowly diminishes with magnesium content, the grain boundary conductivity does not notably depend on the composition.
Добавил в систему: Дейнеко Дина Валерьевна

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Influence of magnesium on dielectric properties of Ca9–xMgxBi(VO4)7 ceramicsстатья Исследовательская статья

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