Synthesis, crystal structure and physicochemical properties of novel calcium doped rare-earth titanium-niobates Nd1-xCaxTi1-xNb1+xO6

Zhelunitsyn, I.A.; Mikhaylovskaya, Z.A.; Votyakov, S.L.

Авторы: Zhelunitsyn Ivan A., Mikhaylovskaya Zoya A., Votyakov Sergey L.
Журнал: Ceramics International
Том: 51
Номер: 22
Год издания: 2025
Издательство: Pergamon Press Ltd.
Местоположение издательства: United Kingdom
Первая страница: 37096
Последняя страница: 37109
DOI: 10.1016/j.ceramint.2025.05.419
Аннотация: Calcium doped rare-earth titanium-niobates Nd1-xCaxTi1-xNb1+xO6 (x = 0–0.2) synthesized using a solid-state technique were analyzed by XRD, SEM, XRF, diffusion reflectance, Raman and impedance spectroscopy. Only the orthorhombic aeschynite phase was observed for ceramics with x = 0–0.10; an admixture of the monoclinic phase was detected for those with x = 0.15–0.20. With increasing x, an increase in the degree of distortion of the AO8 (A = Nd, Ca) and BO6 (B=Ti, Nb) polyhedra was recorded. Significant changes in the unit cell volume did not occur. The chemical composition was close to the theoretical one; the particle size varied from 1 to 10 μm. The optical diffuse reflectance spectra showed f-f transitions of Nd3+ ion, as well as the charge transfer band(s) O2p→Nd 4f and (or) →Nb 4d; the band gap Eg was 3.56–3.63 eV. Raman spectra were typical for the orthorhombic structure of aeschynite. The lines in the ranges of 60–170, 170–340, 340–520, and 520 - 880 cm−1 were associated with Nd-O vibrational modes, (Ti,Nb)O6 bending, tilting and stretching modes, respectively. With increasing x, low- and high-frequency shifts were typical for the lines 60–340 and 340 - 880 cm−1, respectively. The equivalent circuit method was used to process the impedance spectra. The presence of two linearity regions on the Arrhenius dependence of conductivity was revealed. Based on measurements on direct current in Ar, a high contribution of the ionic component of conductivity was assumed. The values of the activation energy Ea were calculated; relaxation processes and dielectric properties of aeschynite were considered. The value of the dielectric constant for the Nd0.9Ca0.1Ti0.9Nb1.1O6 composition was found to be the highest (εr = 44), which, together with the low values of electrical conductivity, opens up prospects for its use as a dielectric material.
Добавил в систему: Желуницын Иван Александрович

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Synthesis, crystal structure and physicochemical properties of novel calcium doped rare-earth titanium-niobates Nd1-xCaxTi1-xNb1+xO6статья