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. 2023 Jun 13;13(6):598.
doi: 10.3390/membranes13060598.

Synthesis and Oxygen Mobility of Bismuth Cerates and Titanates with Pyrochlore Structure

Yuliya Bespalko  1 , Nikita Eremeev  1 , Ekaterina Sadovskaya  1 , Tamara Krieger  1 , Olga Bulavchenko  1 , Evgenii Suprun  1 , Mikhail Mikhailenko  2 , Mikhail Korobeynikov  3 , Vladislav Sadykov  1
Affiliations

Synthesis and Oxygen Mobility of Bismuth Cerates and Titanates with Pyrochlore Structure

Yuliya Bespalko et al. Membranes (Basel). .

Abstract

Synthesis and study of materials based on bismuth cerates and titanates were carried out. Complex oxides Bi1.6Y0.4Ti2O7 were synthesized by the citrate route; Bi2Ce2O7 and Bi1.6Y0.4Ce2O7-by the Pechini method. The structural characteristics of materials after conventional sintering at 500-1300 °C were studied. It is demonstrated that the formation of a pure pyrochlore phase, Bi1.6Y0.4Ti2O7, occurs after high-temperature calcination. Complex oxides Bi2Ce2O7 and Bi1.6Y0.4Ce2O7 have a pyrochlore structure formed at low temperatures. Yttrium doping of bismuth cerate lowers the formation temperature of the pyrochlore phase. As a result of calcination at high temperatures, the pyrochlore phase transforms into the CeO2-like fluorite phase enriched by bismuth oxide. The influence of radiation-thermal sintering (RTS) conditions using e-beams was studied as well. In this case, dense ceramics are formed even at sufficiently low temperatures and short processing times. The transport characteristics of the obtained materials were studied. It has been shown that bismuth cerates have high oxygen conductivity. Conclusions are drawn about the oxygen diffusion mechanism for these systems. The materials studied are promising for use as oxygen-conducting layers in composite membranes.

Keywords: bismuth cerate; bismuth titanate; oxygen mobility; oxygen separation membranes; pyrochlores.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
XRD patterns of Bi2Ce2O7 (a) and Bi1.6Y0.4Ce2O7 (b) obtained by conventional sintering at various temperatures.
Figure 2
Figure 2
IR spectra of Bi2Ce2O7 (a) and Bi1.6Y0.4Ce2O7 (b) obtained by conventional sintering at various temperatures.
Figure 3
Figure 3
XRD patterns of Bi1.6Y0.4Ti2O7 sintered at various temperatures using conventional sintering (a) and radiation-thermal sintering at 1100 °C (b).
Figure 4
Figure 4
IR (a) and RAMAN (b) spectra of Bi1.6Y0.4Ti2O7 samples sintered at various temperatures using conventional sintering.
Figure 5
Figure 5
SEM micrographs of Bi2Ce2O7 (a) and Bi1.6Y0.4Ce2O7 (b) obtained by conventional sintering at 1100 °C.
Figure 6
Figure 6
SEM micrographs of Bi1.6Y0.4Ti2O7 obtained by conventional sintering at 1300 °C for 10 h (a,b), at 1100 °C for 10 h (c,d), and radiation-thermal sintering at 1100 °C for 30 min (e,f).
Figure 7
Figure 7
Temperature-programmed isotope exchange of oxygen with C18O2 in a flow reactor for bismuth cerate and titanate samples sintered at 700 °C. Points—experiment, lines—modeling.
Figure 8
Figure 8
Arrhenius plots for oxygen tracer diffusion coefficients acquired by TPIE data modeling for Bi2Ce2O7 (1), Bi1.6Y0.4Ce2O7 (2), and Bi1.6Y0.4Ti2O7 (3) samples sintered at 700 °C compared to other oxide materials: Bi1.6Sc0.2Ti2O7−δ (4) [26], Bi1.6Mg0.2Ti2O7−δ (5) [26], Bi1.6Zn0.2Ti2O7−δ (6) [20], Zr0.84Y0.16O1.92 (7) [49], La0.8Sr0.2MnO3−δ (8) [50], La0.5Sr0.5Fe0.7Co0.3O3−δ (9) [51].
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