Details

Autor(en) / Beteiligte

• Zhuk, Nadezhda A
• Krzhizhanovskaya, Maria G
• Koroleva, Alexandra V
• Sekushin, Nikolay A
• Nekipelov, Sergey V
• Kharton, Vladislav V
• Makeev, Boris A
• Lutoev, Vladimir P
• Sennikova, Yana D

Titel

Cu, Mg Codoped Bismuth Tantalate Pyrochlores: Crystal Structure, XPS Spectra, Thermal Expansion, and Electrical Properties

Ist Teil von

• Inorganic chemistry, 2022-03, Vol.61 (10), p.4270-4282

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2022

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The pyrochlore-type solid-solution formation in a Bi1.6Mg0.8–x Cu x Ta1.6O7.2−Δ 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−Δ, 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 Fd3̅m: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–x Cu x Ta1.6O7.2−Δ 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.