A study of phase evolution of Fe-doped bismuth tantalate pyrochlore

Жук, Н. А.; Макеев, Б. А.; Korolev, R.I.; Sivkov, D.N.; Shpynova, A.D.

doi:10.1016/j.ceramint.2022.07.132

Cited by 1 publication

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“…For the pyrochlore Bi 1.5 ZnTa 1.5 O 7 , the permittivity is 58 [27,28]. The electrical characteristics of cobalt pyrochlores are comparable to those of nickel-and magnesiumcontaining preparations of the similar composition Bi 2 Mg(Ni)Ta 2 O 9 , the permittivity and dielectric loss tangent of which are 20 (32) and 2 × 10 −3 (6 × 10 −2 ) at RT and a frequency of 1 MHz [29,30]. As shown in [31], Bi 2 Mg 1−x Ni x Ta 2 O 9 (x = 0.3, 0.5, 0.7) samples are insulators, with high activation energies of ~2.0 eV, average values of permittivity (~24-28) and a dielectric loss of ~0.002 at 1 MHz and 21 • C.…”

Section: Introductionmentioning

confidence: 85%

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Phase Formation of Co and Cr Co-Doped Bismuth Niobate with Pyrochlore Structure

Zhuk,

Badanina,

Korolev

et al. 2023

Inorganics

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The formation mechanisms of pyrochlore-type Bi2Co1/2Cr1/2Nb2O9+Δ (space group Fd-3m, a = 10.4838(8) Å), in the temperature range from 400 to 1050 °C were studied by employing X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. An extensive reaction between the binary metal oxides was found to begin at temperatures above 550 °C, following the transition of monoclinic α-Bi2O3 into a tetragonal β-Bi2O3 polymorph. The synthesis process occurs in several stages when Bi-rich intermediate products (Bi6CrO12, Bi6Cr2O15, and Bi5Nb3O15) transform into bismuth-depleted BiNbO4 and a chromium–cobalt spinel is formed. The formation of a single pyrochlore phase occurs at the final reaction stage at 1050 °C via the doping of bismuth ortho-niobate, BiNbO4, by the transition metal cations. The observed mechanism is essentially similar to the mechanism of tantalate-based phases except for the formation of Bi5Nb3O15 at the intermediate reaction stages.

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Section: Introductionmentioning

confidence: 85%

“…Investigations of the pyrochlore phase formation mechanisms in these materials revealed key stages of the solid-state reactions, including the appearance of α-BiTaO 4 as an intermediate product transforming into pyrochlore [32][33][34][35][36]. In the case of chromium doping, intermediate phases containing Cr(VI) were found to form [35].…”

Section: Introductionmentioning

confidence: 99%