Ternary molybdate K5Cu0.5Hf1.5(MoO4)6: synthesis, structure, thermal expansion and ionic conductivity

  • Evgeniy V. Kovtunets Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0003-1301-1983
  • Tatiyana S. Spiridonova Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0001-7498-5103
  • Yunna L. Tushinova Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0003-1032-8854
  • Tsyrendyzhit T. Bazarova Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0001-9697-6320
  • Alexandra V. Logvinova Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0001-9850-2719
  • Bair G. Bazarov Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation https://orcid.org/0000-0003-1712-6964
DOI: https://doi.org/10.17308/kcmf.2025.27/13014
Keywords: Potassium, copper, Hafnium, Ternary molybdate, Synthesis, Crystal structure, Thermal expansion, Ionic conductivity

Abstract

Objective: A novel ternary molybdate, K5Cu0.5Hf1.5(MoO4)6, was synthesized using solid-state ceramic method. The sequence of chemical transformations involved in its formation was determined, revealing that the compound undergoes incongruent melting at 634 °C.

Experimental: The crystal structure was refined using the Rietveld method, revealing a trigonal structure (space group R3c) with unit cell parameters a = 10.5617(2) Å; c = 37.5017(7) Å; V= 3622.9(1) Å3, Rwp = 3.78. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy confirmed the presence of isolated MoO4 tetrahedra. The electrical conductivity of the title compound reached 7.5·10–4 S/cm at 550°C, with an activation energy Еа = 0.9 eV. Thermal deformations were investigated by high temperature powder X-ray diffraction (HT-XRD) over the temperature range of 30–500 °C.

Results: K5Cu0.5Hf1.5(MoO4)6 was classified as a high thermal expansion material (αV = 45·10–6 °C–1 at 500 °C), and exhibited low anisotropy. Combined results from electrochemical impedance spectroscopy (EIS) and HT-XRD indicated that the endothermic peak observed at 479 °С in the differential scanning calorimetry (DSC) curve corresponded to a first-order phase transition

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Author Biographies

Evgeniy V. Kovtunets, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Cand. Sci. (Phys.–Math.), Researcher, Laboratory of Oxide Systems, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

Tatiyana S. Spiridonova, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Cand. Sci. (Chem.), Senior Researcher, Laboratory of Oxide Systems, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

Yunna L. Tushinova, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Cand. Sci. (Chem.), Researcher, Laboratory of Oxide Systems, Baikal Institute of Nature
Management, Siberian Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

Tsyrendyzhit T. Bazarova, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Cand. Sci. (Chem.), Lead Engineer, Laboratory of Oxide Systems, Baikal Institute of
Nature Management, Siberian Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

Alexandra V. Logvinova, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Engineer, Laboratory of Oxide Systems, Baikal Institute of Nature Management, Siberian
Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

Bair G. Bazarov, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, 6, Sakhyanova str., 670047 Ulan-Ude, Republic of Buryatia, Russian Federation

Dr. Sci. (Phys.–Math.), Leading Researcher, Laboratory of Oxide Systems, Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences (Ulan-Ude, Russian Federation)

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Published
2025-09-25
How to Cite
Kovtunets, E. V., Spiridonova, T. S., Tushinova, Y. L., Bazarova, T. T., Logvinova, A. V., & Bazarov, B. G. (2025). Ternary molybdate K5Cu0.5Hf1.5(MoO4)6: synthesis, structure, thermal expansion and ionic conductivity. Kondensirovannye Sredy I Mezhfaznye Granitsy = Condensed Matter and Interphases, 27(3), 380-390. https://doi.org/10.17308/kcmf.2025.27/13014
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Vol 27 No 3 (2025)
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