TY - JOUR

T1 - Cu, Mg Codoped Bismuth Tantalate Pyrochlores

T2 - Crystal Structure, XPS Spectra, Thermal Expansion, and Electrical Properties

AU - Zhuk, Nadezhda A.

AU - Krzhizhanovskaya, Maria G.

AU - Koroleva, Alexandra V.

AU - Sekushin, Nikolay A.

AU - Nekipelov, Sergey V.

AU - Kharton, Vladislav V.

AU - Makeev, Boris A.

AU - Lutoev, Vladimir P.

AU - Sennikova, Yana D.

N1 - Publisher Copyright: © 2022 American Chemical Society.

PY - 2022/3/14

Y1 - 2022/3/14

N2 - The pyrochlore-type solid-solution formation in a Bi1.6Mg0.8-xCuxTa1.6O7.2- system, synthesized for the first time, is observed at x ≤ 0.56. High-temperature X-ray diffraction showed that the pyrochlore phase exists in air up to 1080 °C, where its thermal decomposition leads to the segregation of (Mg,Cu)Ta2O6. The thermal expansion coefficients of the end member, Bi1.6Mg0.24Cu0.56Ta1.6O7.2-, increase from 3.3 × 10-6 °C-1 at room temperature up to 8.7 × 10-6 °C-1 at 930 °C. Rietveld refinement confirmed that the pyrochlore crystal structure is disordered with space group Fd3¯ m:2 (Z = 8, no. 227). Doping with copper results in a modest expansion of the cubic unit cell, promotes sintering of the ceramic materials, and induces their red-brown color. X-ray photoelectron spectroscopy demonstrated that the states of Bi(III) and Mg(II) are not affected by doping, and the effective charge of tantalum cations is lower than +5, while the Cu(II) states coexist with Cu(I). The electron spin resonance spectra display a single line with g = 2.2, ascribed to the dipole-broadened Cu2+ signal. The dielectric permittivity of Bi1.6Mg0.8-xCuxTa1.6O7.2- ceramics may achieve up to 105, with the dielectric loss tangent varying in the range from 0.2 up to 12. Multiple dielectric relaxations are found at room temperature and above for all samples.

AB - The pyrochlore-type solid-solution formation in a Bi1.6Mg0.8-xCuxTa1.6O7.2- system, synthesized for the first time, is observed at x ≤ 0.56. High-temperature X-ray diffraction showed that the pyrochlore phase exists in air up to 1080 °C, where its thermal decomposition leads to the segregation of (Mg,Cu)Ta2O6. The thermal expansion coefficients of the end member, Bi1.6Mg0.24Cu0.56Ta1.6O7.2-, increase from 3.3 × 10-6 °C-1 at room temperature up to 8.7 × 10-6 °C-1 at 930 °C. Rietveld refinement confirmed that the pyrochlore crystal structure is disordered with space group Fd3¯ m:2 (Z = 8, no. 227). Doping with copper results in a modest expansion of the cubic unit cell, promotes sintering of the ceramic materials, and induces their red-brown color. X-ray photoelectron spectroscopy demonstrated that the states of Bi(III) and Mg(II) are not affected by doping, and the effective charge of tantalum cations is lower than +5, while the Cu(II) states coexist with Cu(I). The electron spin resonance spectra display a single line with g = 2.2, ascribed to the dipole-broadened Cu2+ signal. The dielectric permittivity of Bi1.6Mg0.8-xCuxTa1.6O7.2- ceramics may achieve up to 105, with the dielectric loss tangent varying in the range from 0.2 up to 12. Multiple dielectric relaxations are found at room temperature and above for all samples.

UR - http://www.scopus.com/inward/record.url?scp=85126385339&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/248b8465-e554-3a43-9398-81dbf832f239/

U2 - 10.1021/acs.inorgchem.1c03053

DO - 10.1021/acs.inorgchem.1c03053

M3 - Article

C2 - 35239334

AN - SCOPUS:85126385339

VL - 61

SP - 4270

EP - 4282

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 10

ER -