Synthesis and physical properties of pyrochlore cobalt oxides Bi1.56-xCaxSb1.48Co0.96O7-δ

Sellami, M.; Zouaoui, K.; Talbi, B.; Mekki-Douadji, C.; Berahal, M.; Merabet, F.; Ezziane, K.

doi:10.1590/0366-69132023693903404

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Articles • Cerâmica 69 (390) • Apr-Jun 2023 • https://doi.org/10.1590/0366-69132023693903404 copy

Synthesis and physical properties of pyrochlore cobalt oxides Bi_1.56-xCa_xSb_1.48Co_0.96O_7-δ

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

A new solid solution Bi_1.56-xCa_xSb_1.48Co_0.96O_7-δ (0≤x≤0.3) with a pyrochlore-like structure (A₂B₂O₇) was synthesized in air by chemical solid-state reaction. The solution crystallized in the cubic system with the Fd-3m space group. A regular decrease of the lattice parameter was observed when calcium replaced bismuth in the A site. The electric measurements showed that the electrical conductivity increased with the temperature and that high values of relative permittivity and dielectric loss were put in evidence. Measurements of magnetic susceptibility indicated a paramagnetic behavior of the samples with an effective moment included between 4.81 and 5.12 μ_B and at a low temperature para-ferromagnetic transition was observed for fractions x= 0.2 and 0.3.

Keywords:
pyrochlore; bismuth; cobalt; calcium; solid solution; X-ray; electrical conductivity; magnetic susceptibility

Fraction x	Formula	δ
0	$({Bi}_{1.56}^{3 +} {Co}_{0.44}^{2 +}) ({Sb}_{1.48}^{5 +} {Co}_{0.52}^{2 +}) O_{7}^{2 -}$	0
0.10	$({Bi}_{1.46}^{3 +} C a_{0.1}^{2 +} {Co}_{0.44}^{2 +}) ({Sb}_{1.48}^{5 +} {Co}_{0.52}^{2 +}) O_{6.95}^{2 -}$	0.050
0.20	$({Bi}_{1.36}^{3 +} C a_{0.2}^{2 +} {Co}_{0.44}^{2 +}) ({Sb}_{1.48}^{5 +} {Co}_{0.52}^{2 +}) O_{6.9}^{2 -}$	0.100
0.25	$({Bi}_{1.31}^{3 +} C a_{0.25}^{2 +} {Co}_{0.44}^{2 +}) ({Sb}_{1.48}^{5 +} {Co}_{0.52}^{2 +}) O_{6.875}^{2 -}$	0.125
0.30	$({Bi}_{1.2}^{3 +} C a_{0.3}^{2 +} {Co}_{0.44}^{2 +}) ({Sb}_{1.48}^{5 +} {Co}_{0.52}^{2 +}) O_{6.85}^{2 -}$	0.150

Fraction x	μ_eff/mol Co (μ_B)
x=0.0	4.78
x=0.2	5.06
x=0.3	4.72

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