TY - JOUR

T1 - Thermal expansion, crystal structure, XPS and NEXAFS spectra of Fe-doped bismuth tantalate pyrochlore

AU - Zhuk, N. A.

AU - Krzhizhanovskaya, M. G.

AU - Koroleva, A. V.

AU - Reveguk, A. A.

AU - Sivkov, D. V.

AU - Nekipelov, S. V.

N1 - Publisher Copyright: © 2022 Elsevier Ltd and Techna Group S.r.l.

PY - 2022/5/15

Y1 - 2022/5/15

N2 - The thermal behavior, crystal structure and charge state of ions in the composition of a new pyrochlore Bi1.6Fe0.8Ta1.6O7.6 (refined formula Bi1.50Fe0.60Ta1.40O6.77) synthesized via standard ceramic method are studied. The disordered pyrochlore structural parameters were obtained by the Rietveld method (sp. gr. Fd-3m:2 (227), 10.49689(3) Å, Z = 8). Iron (III) ions occupy octahedral positions of tantalum (V). The sample is characterized by a loose microstructure formed by partially fused grains with a longitudinal size of 0.2–2 μm. Using the high-temperature x-ray diffractometry method it was found that Fe-doped bismuth tantalate pyrochlore is thermally stable up to a temperature of ∼1140 °C. The unit cell parameter a and coefficient of thermal expansion (TEC) uniformly weakly increase from 10.4796 Å to 10.5603 Å and from 4.5 × 10−6 °C−1 to 9.2 × 10−6 °C−1, respectively, in the temperature range of 30 ÷ 1050 °C. This behavior is typical for frame structures of the pyrochlore type. The pyrochlore thermal behavior in the low-temperature region (−170 ÷ 100 °C) is characterized by high growth of TEC from 1.3 × 10−6 °C−1 (−170 °C) to 4.6 × 10−6 °C−1 (100 °C) with respect to a weak increase in a from 10.48627 (−70 °C) to 10.49444 Å(100 °C). According to the data of near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy, the ion charge states were determined as Bi (III), Ta(V), Fe(III).

AB - The thermal behavior, crystal structure and charge state of ions in the composition of a new pyrochlore Bi1.6Fe0.8Ta1.6O7.6 (refined formula Bi1.50Fe0.60Ta1.40O6.77) synthesized via standard ceramic method are studied. The disordered pyrochlore structural parameters were obtained by the Rietveld method (sp. gr. Fd-3m:2 (227), 10.49689(3) Å, Z = 8). Iron (III) ions occupy octahedral positions of tantalum (V). The sample is characterized by a loose microstructure formed by partially fused grains with a longitudinal size of 0.2–2 μm. Using the high-temperature x-ray diffractometry method it was found that Fe-doped bismuth tantalate pyrochlore is thermally stable up to a temperature of ∼1140 °C. The unit cell parameter a and coefficient of thermal expansion (TEC) uniformly weakly increase from 10.4796 Å to 10.5603 Å and from 4.5 × 10−6 °C−1 to 9.2 × 10−6 °C−1, respectively, in the temperature range of 30 ÷ 1050 °C. This behavior is typical for frame structures of the pyrochlore type. The pyrochlore thermal behavior in the low-temperature region (−170 ÷ 100 °C) is characterized by high growth of TEC from 1.3 × 10−6 °C−1 (−170 °C) to 4.6 × 10−6 °C−1 (100 °C) with respect to a weak increase in a from 10.48627 (−70 °C) to 10.49444 Å(100 °C). According to the data of near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy, the ion charge states were determined as Bi (III), Ta(V), Fe(III).

KW - Bismuth tantalate pyrochlore

KW - Fe doping

KW - NEXAFS

KW - Thermal expansion

KW - XPS

UR - http://www.scopus.com/inward/record.url?scp=85124558324&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/d46a2795-e810-32e4-8808-54feebf9daf7/

U2 - 10.1016/j.ceramint.2022.02.021

DO - 10.1016/j.ceramint.2022.02.021

M3 - Article

AN - SCOPUS:85124558324

VL - 48

SP - 14849

EP - 14855

JO - Ceramics International

JF - Ceramics International

SN - 0272-8842

IS - 10

ER -