Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate
The powders of Ca1–2xBi2xMo1–xGexO4 solid solutions weresynthesized by the conventional solid state method and investigated by X–ray powder diffraction and Raman spectroscopy. The Ca1–2xBi2xMo1–xGexO4 compositions crystallize in scheelite structure (sp. gr. I41/a) at 0 x 0.4, but traces of bismuth...
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| Format: | Article |
| Language: | English |
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Uralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. Elʹcina
2022-08-01
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| Series: | Chimica Techno Acta |
| Subjects: | |
| Online Access: | https://journals.urfu.ru/index.php/chimtech/article/view/6079 |
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| author | Zoya A. Mikhaylovskaya Elena S. Buyanova Sofia A. Petrova Elizaveta A. Pankrushina Alexander I. Malkin Alexey N. Korotkov Nikolay S. Knyazev |
| author_facet | Zoya A. Mikhaylovskaya Elena S. Buyanova Sofia A. Petrova Elizaveta A. Pankrushina Alexander I. Malkin Alexey N. Korotkov Nikolay S. Knyazev |
| author_sort | Zoya A. Mikhaylovskaya |
| collection | DOAJ |
| description | The powders of Ca1–2xBi2xMo1–xGexO4 solid solutions weresynthesized by the conventional solid state method and investigated by X–ray powder diffraction and Raman spectroscopy. The Ca1–2xBi2xMo1–xGexO4 compositions crystallize in scheelite structure (sp. gr. I41/a) at 0 x 0.4, but traces of bismuth germanates are detected by scanning electron microscopy. The x = 0.5 composition contains several phases with BiVO4- type structures. Raman spectroscopy detected the deformation of [BO4]2– polyhedra and changes in B–O bond length (B = Mo, Ge). The energy gaps were calculated from the diffuse scattering spectra by the Kubelka-Munk method. Energy gap (Eg) values decrease with x from 3.29 eV to 2.91 eV, probably due to 6s2 electrons of bismuth in the valence band and changes of the conductivity band by electrons of germanium. Such values of Eg can provide photocatalytical activity of powders under UV and visible light. The electrodynamic parameters of the ceramic sample of Ca1–2xBi2xMo1–xGexO4 were measured by the transmission line method. The average permittivity increases with x from ~10 to ~18 which correlates with theoretical ε, Vmol and total polarizability of samples. An increase in the concentration of bismuth and germanium leads to the additional resonant peaks in the spectra of ε, S11 and S21. These resonant peaks can be probably caused by the appearance of irregular structural domains of Bi atoms or induced by the increased size of grains in the ceramic samples. |
| first_indexed | 2024-04-09T17:13:11Z |
| format | Article |
| id | doaj.art-d69cbb8892064ca597e5f8298c2351c0 |
| institution | Directory Open Access Journal |
| issn | 2411-1414 |
| language | English |
| last_indexed | 2024-04-09T17:13:11Z |
| publishDate | 2022-08-01 |
| publisher | Uralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. Elʹcina |
| record_format | Article |
| series | Chimica Techno Acta |
| spelling | doaj.art-d69cbb8892064ca597e5f8298c2351c02023-04-20T04:42:06ZengUralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. ElʹcinaChimica Techno Acta2411-14142022-08-019410.15826/chimtech.2022.9.4.114546Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdateZoya A. Mikhaylovskaya0Elena S. Buyanova1Sofia A. Petrova2Elizaveta A. Pankrushina3Alexander I. Malkin4Alexey N. Korotkov5Nikolay S. Knyazev6Zavaritsky Institute of Geology and Geochemistry, UB RAS; Ural Federal UniversityZavaritsky Institute of Geology and Geochemistry, UB RAS; Ural Federal UniversityInstitute of Metallurgy, UB RASZavaritsky Institute of Geology and Geochemistry, UB RASUral Federal UniversityUral Federal UniversityUral Federal UniversityThe powders of Ca1–2xBi2xMo1–xGexO4 solid solutions weresynthesized by the conventional solid state method and investigated by X–ray powder diffraction and Raman spectroscopy. The Ca1–2xBi2xMo1–xGexO4 compositions crystallize in scheelite structure (sp. gr. I41/a) at 0 x 0.4, but traces of bismuth germanates are detected by scanning electron microscopy. The x = 0.5 composition contains several phases with BiVO4- type structures. Raman spectroscopy detected the deformation of [BO4]2– polyhedra and changes in B–O bond length (B = Mo, Ge). The energy gaps were calculated from the diffuse scattering spectra by the Kubelka-Munk method. Energy gap (Eg) values decrease with x from 3.29 eV to 2.91 eV, probably due to 6s2 electrons of bismuth in the valence band and changes of the conductivity band by electrons of germanium. Such values of Eg can provide photocatalytical activity of powders under UV and visible light. The electrodynamic parameters of the ceramic sample of Ca1–2xBi2xMo1–xGexO4 were measured by the transmission line method. The average permittivity increases with x from ~10 to ~18 which correlates with theoretical ε, Vmol and total polarizability of samples. An increase in the concentration of bismuth and germanium leads to the additional resonant peaks in the spectra of ε, S11 and S21. These resonant peaks can be probably caused by the appearance of irregular structural domains of Bi atoms or induced by the increased size of grains in the ceramic samples.https://journals.urfu.ru/index.php/chimtech/article/view/6079calcium molybdatebismuth molybdatemicrowave dielectricraman spectroscopyenergy gap |
| spellingShingle | Zoya A. Mikhaylovskaya Elena S. Buyanova Sofia A. Petrova Elizaveta A. Pankrushina Alexander I. Malkin Alexey N. Korotkov Nikolay S. Knyazev Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate Chimica Techno Acta calcium molybdate bismuth molybdate microwave dielectric raman spectroscopy energy gap |
| title | Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate |
| title_full | Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate |
| title_fullStr | Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate |
| title_full_unstemmed | Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate |
| title_short | Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate |
| title_sort | structure and microwave dielectric properties of bi and ge doped calcium molybdate |
| topic | calcium molybdate bismuth molybdate microwave dielectric raman spectroscopy energy gap |
| url | https://journals.urfu.ru/index.php/chimtech/article/view/6079 |
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