Pyrochlore phase in the Bi₂O₃‒Fe₂O₃‒WO₃‒(H₂O) system: its stability field in the low-temperature region of the phase diagram and thermal stability

The concentration stability field localization of the pyrochlore-structured compounds of variable composition formed in the Bi₂O₃–Fe₂O₃–WO₃ system under hydrothermal conditions at a temperature of T = 200◦C and a pressure of P = 7 MPa was determined. It was found that the pyrochlore-structured compounds stability field is longitudinally limited within the atomic ratios 0.47 < Bi/W < 1.25, and in the transverse direction within 1.14 < Bi/Fe < 1.87. It was shown that the pyrochlore phase cubic unit cell parameter a depends on the compound chemical composition as follows: it increases linearly from ∼ 10.3319 A˚ to ∼ 10.4199 A˚ with an increase in the Bi/W atomic ratio from ∼ 0.47 to ∼ 1.25. It was established that from the Bi₂O₃–WO₃ system side, there is a region of two-phase equilibrium, in which a pyrochlore phase of variable composition coexists with the Bi2WO6 compound, which is formed in the form of plate-like (thickness h ∼ 50–100 nm) nanoparticles. It was shown that from the Bi₂O₃–Fe₂O₃ system side, there is a region of compositions, in which the pyrochlore phase of the most enriched in bismuth oxide composition coexists with the Bi₂WO₆ compound, which is formed in the form of rod-shaped (h ∼ 10–30 nm) nanoparticles, and with the X-ray amorphous phase composition, formed in the form of nanocrystalline particles about 10 nm in size. It was found that the higher temperature point of the pyrochlore-structured compounds stability field does not exceed 725◦C, which allows them to be synthesized only by “soft chemistry” methods.

1. Ellert O.G., Egorysheva A.V., Gajtko O.M., Kirdyankin D.I., Svetogorov R.D. Highly Frustrated Bi–Cr–Sb–O Pyrochlore with Spin-Glass Transition. Journal of Magnetism and Magnetic Materials, 2018, 463, P. 13–18.

2. Egorysheva A.V., Ellert O.G., Maksimov Y.V., Volodin V.D., Efimov N.N., Novotortsev V.M. Subsolidus Phase Equilibria and Magnetic Characterization of the Pyrochlore in the Bi2O3–Fe2O3–Sb2Ox System. Journal of Alloys and Compounds, 2013, 579, P. 311–314.

3. Koroleva M.S., Piir I.V., Ryabkov Yu.I., Korolev D.A., Chezhina N.V. Synthesis and Properties of Chromium-Containing Bismuth Titanates with the Pyrochlore Structure. Russian Chemical Bulletin, International Edition, 2013, 62(2), P. 408–411.

4. Babu G.S., Bedanta S., Valant M. Evidence of the spin glass state in (Bi1.88Fe0.12)(Fe1.42Te0.58)O6.87 pyrochlore. Solid State Communications, 2013, 158, P. 51–53.

5. Lufaso M.W., Vanderah T.A., Pazos I.M., Levin I., Roth R.S., Nino J.C., Provenzano V., Schenck P.K. Phase Formation, Crystal Chemistry, and Properties in the System Bi2O3–Fe2O3–Nb2O5. Journal of Solid State Chemistry, 2006, 179(12), P. 3900–3910.

6. Jusoh F.A., Tan K.B., Zainal Z., Chen S.K., Khaw C.C., Lee O.J. Novel pyrochlores in the Bi2O3-Fe2O3-Ta2O5 (BFT) Ternary System: Synthesis, Structural and Electrical Properties. Journal of Materials Research and Technology, 2020, 9(5), P. 11022–11034.

7. Liu W., Wang H. Enhanced Dielectric Properties of Bi1.5ZnNb1.5O7 Thick Films via Cold Isostatic Pressing. Journal of Electroceramics, 2012, 29(3), P. 183–186.

8. Piir I.V., Koroleva M.S., Ryabkov Y.I., Korolev D.A., Chezhina N.V., Semenov V.G., Panchuk V.V. Bismuth Iron Titanate Pyrochlores: Thermostability, Structure and Properties. Journal of Solid State Chemistry, 2013, 204, P. 245–250.

9. Krasnov A.G., Piir I.V., Koroleva M.S., Sekushin N.A., Ryabkov Y.I., Piskaykina M.M., Sadykov V.A., Sadovskaya E.M., Pelipenko V.V., Eremeev N.F. The Conductivity and Ionic Transport of Doped Bismuth Titanate Pyrochlore Bi1.6MxTi2O7−δ (M-Mg, Sc, Cu). Solid State Ionics, 2017, 302, P. 118–125.

10. Egorysheva A.V., Gajtko O.M., Rudnev P.O., Ellert O.G., Ivanov V.K. Synthesis of Bi-Fe-Sb-O Pyrochlore Nanoparticles with Visible-Light Photocatalytic Activity. European Journal of Inorganic Chemistry, 2016, 13–14, P. 2193–2199.

11. Bencina M., Valant M., Pitcher M.W., Fanetti M. Intensive Visible-Light Photoactivity of Bi- and Fe-Containing Pyrochlore Nanoparticles. Nanoscale, 2014, 6(2), P. 745–748.

12. Allured B., DelaCruz S., Darling T., Huda M.N., Subramanian V.(R.) Enhancing the visible light absorbance of Bi2Ti2O7 through Fe-substitution and its effects on photocatalytic hydrogen evolution. Appl. Catal. B Environ, 2014, 144, P. 261–268.

13. Pyrochlorine Materials and thermal barrier coating with these pyrochlore materials, Patent. 2454477 Russia: MPK C22C 29/12, C23C 30/00, Malov T., Oexchep M., N 2009116606/02, Issue N 18, 27.06.2012.

14. Xue J., Zhang K., He Z., Zhao W., Li W., Xie D., Luo B., Xu K., Zhang H. Rapid Immobilization of Simulated Radioactive Soil Waste Using Self-Propagating Synthesized Gd2Ti2O7 Pyrochlore Matrix. Materials, 2019, 12(7), P. 1163.

15. Benčina M., Valant M. Bi2Ti2O7-based pyrochlore nanoparticles and their superior photocatalytic activity under visible light. Journal of the American Ceramic Society, 2017, 101(1), P. 82–90.

16. Castellano C., Berti G., Rubio-Marcos F., Lamura G., Sanna S., Salas-Colera E., Brambilla A., Muñoz-Noval Á., Duò L., Demartin F. Anomalous local lattice disorder and distortion in A2Mo2O7 pyrochlores. Journal of Alloys and Compounds, 2017, 723, P. 327–332.

17. Zhuk N.A., Krzhizhanovskaya M.G., Koroleva A.V., Semenov V.G., Selyutin A.A., Lebedev A.M., Nekipelov S.V., Sivkov D.V., Kharton V.V., Lutoev V.P., Makeev B.A. Fe,Mg-Codoped Bismuth Tantalate Pyrochlores: Crystal Structure, Thermal Stability, Optical and Electrical Properties, XPS, NEXAFS, ESR, and 57Fe Mössbauer Spectroscopy Study. Inorganics, 2023, 11(1), P. 8.

18. Guskov V.N., Gagarin P.G., Tyurin A.V., Khoroshilov A.V., Guskov A.V., Gavrichev K.S. Heat capacity of solutions LaLnZr2O7 (Ln = Sm, Gd, Dy) with the structure of pyrochlore in the temperature range of 10–1400 K. Russian Journal of Physical Chemistry A, 2020, 94(2), P. 233–239.

19. Lomakin M.S., Proskurina O.V., Gusarov V.V. Pyrochlore phase in the Bi2O3–Fe2O3–WO3?(H2O) system: its formation by hydrothermal synthesis in the low-temperature region of the phase diagram. Nanosystems: Phys. Chem. Math., 2023, 14(2), P. 242–253.

20. Lomakin M.S., Proskurina O.V., Levin A.A., Sergeev A.A., Leonov A.A., Nevedomsky V.N., Voznesenskiy S.S. Pyrochlore Phase in the Bi2O3– Fe2O3–WO3–(H2O) System: its Formation by Hydrothermal-Microwave Synthesis and Optical Properties. Russ. J. Inorg. Chem. 2022, 67(6), P. 820–829.

21. Lomakin M.S., Proskurina O.V., Abiev R.Sh., Nevedomskiy V.N., Leonov A.A., Voznesenskiy S.S., Gusarov V.V. Pyrochlore phase in the Bi2O3– Fe2O3–WO3–(H2O) system: physicochemical and hydrodynamic aspects of its production using a microreactor with intensively swirled flows. Advanced Powder Technology, 2023, 34(7), 104053.

22. Daniels L.M., Playford H.Y., Grenèche J.-M., Hannon A.C., Walton R.I. Metastable (Bi, M)2(Fe, Mn, Bi)2O6+x (M = Na or K) Pyrochlores from Hydrothermal Synthesis. Inorganic Chemistry, 2014, 53(24), P. 13197–13206.

23. Egorysheva A.V., Gajtko O.M., Rudnev P.O., Ellert O.G., Ivanov V.K. Synthesis of Bi–Fe–Sb–O Pyrochlore nanoparticles with visible-light photocatalytic activity. Eur. J. Inorg. Chem., 2016, 13–14, P. 2193–2199.

24. Radha R., Srinivasan A., Manimuthu P., Balakumar S. Tailored sunlight driven nano-photocatalyst: bismuth iron tungstate (BiFeWO6), J. Mater. Chem. C, 2015, 3(39), P. 10285–10292.

25. Annamalai K., Radha R., Vijayakumari S., Kichanov S.E., Balakumar S. Insight into the investigation on nanostructured defect pyrochlore Bi2−xFexWO6 and its photocatalytic degradation of mixed cationic dyes. Materials Science in Semiconductor Processing, 2022, 150, 2022, P. 106961.

26. Wang Y., Zhang S., Zhong Q., Zeng Y., Ou M., Cai W. Hydrothermal synthesis of novel uniform nanooctahedral Bi3(FeO4)(WO4)2 solid oxide and visible-light photocatalytic performance. Ind. Eng. Chem. Res., 2016, 55(49), P. 12539–12546.

27. Lomakin M.S., Proskurina O.V., Danilovich D.P., Panchuk V.V., Semenov V.G., Gusarov V.V. Hydrothermal Synthesis, Phase Formation and Crystal Chemistry of the pyrochlore/Bi2WO6 and pyrochlore/α-Fe2O3 Composites in the Bi2O3–Fe2O3–WO3System. J. Solid State Chem., 2020, 282, P. 121064.

28. Narykova M.V., Levin A.A., Prasolov N.D., Lihachev A.I., Kardashev B.K., Kadomtsev A.G., Panfilov A.G., Sokolov R.V., Brunkov P.N., Sultanov M.M., Kuryanov V.N., Tyshkevich V.N. The structure of the near-surface layer of the AAAC overhead power line wires after operation and its effect on their elastic, microplastic, and electroresistance properties. Crystals, 2022, 12, P. 166.

29. Fawcett T.G., Kabekkodu S.N., Blanton J.R., Blanton T.N. Chemical analysis by diffraction: the Powder Diffraction File™. Powder Diffr., 2017, 32, P. 63–71.

30. Maunders C., Etheridge J., Wright N., Whitfield H.J. Structure and microstructure of hexagonal Ba3Ti2RuO9 by electron diffraction and microscopy. Acta Crystallogr. B., 2005, 61, P. 154–159.

31. Levin A.A. Program SizeCr for calculation of the microstructure parameters from X-ray diffraction data. preprint ResearchGate, 2022.

32. Terlan B., Levin A.A., Börrnert F., Simon F., Oschatz M., Schmidt M., Cardoso-Gil R., Lorenz T., Baburin I.A., Joswig J.-O., Eychmüller A. Effect of Surface Properties on the Microstructure, Thermal, and Colloidal Stability of VB2 Nanoparticles. Chem. Mater., 2015, 27, P. 5106–5115.

33. Terlan B., Levin A.A., Börrnert F., Zeisner J., Kataev V., Schmidt M., Eychmüller A. A Size-Dependent Analysis of the Structural, Surface, Colloidal, and Thermal Properties of Ti1−xB2 (x = 0.03–0.08) Nanoparticles. Eur. J. Inorg. Chem., 2016, 6, P. 3460–3468.

34. Langford I., Cernik R. J., Louer D. The Breadth and Shape of Instrumental Line Profiles in High-Resolution Powder Diffraction. J. Appl. Phys., 1991, 24, P. 913–919.

35. Scherrer P. Bestimmung der Grösse und der inneren Struktur von Kolloidteilchen mittels Röntgenstrahlen. Nachr. Königl. Ges. Wiss. Göttingen., 1918, 26, P. 98–100. (in German)

36. Stokes A.R., Wilson A.J.C. The diffraction of X-rays by distorted crystal aggregates. Proc. Phys. Soc. London, 1944, 56, P. 174–181.