Thermal properties of rare earth cobalt oxides and of La1–x Gd x CoO3 solid solutions
| Autor: | Yu. S. Orlov, Mikhail V. Gorev, V. A. Dudnikov, L. A. Solov’ev, S. N. Vereshchagin, Sergey Ovchinnikov |
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| Rok vydání: | 2016 |
| Předmět: |
Lanthanide
Equation of state Materials science Physics and Astronomy (miscellaneous) Doping Analytical chemistry chemistry.chemical_element 02 engineering and technology Crystal structure Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences Thermal expansion Condensed Matter::Materials Science chemistry 0103 physical sciences Condensed Matter::Strongly Correlated Electrons 010306 general physics 0210 nano-technology Cobalt Solid solution |
| Zdroj: | JETP Letters. 103:607-612 |
| ISSN: | 1090-6487 0021-3640 |
| DOI: | 10.1134/s0021364016090058 |
| Popis: | Powder X-ray diffraction data for the crystal structure, phase composition, and molar specific heat for La1‒xGdxCoO3 cobaltites in the temperature range of 300–1000 K have been analyzed. The behavior of the volume thermal expansion coefficient in cobaltites with isovalent doping in the temperature range of 100–1000 K is studied. It is found that the β(T) curve exhibits two peaks at some doping levels. The rate of the change in the occupation number for the high-spin state of cobalt ions is calculated for the compounds under study taking into account the spin–orbit interaction. With the Birch–Murnaghan equation of state, it is demonstrated that the low-temperature peak in the thermal expansion shifts with the growth of the pressure toward higher temperatures and at pressure P ∼ 7 GPa coincides with the second peak. The similarity in the behavior of the thermal expansion coefficient in the La1–xGdxCoO3 compounds with the isovalent substitution and the undoped LnCoO3 compound (Ln is a lanthanide) is considered. For the whole series of rare earth cobalt oxides, the nature of two specific features in the temperature dependence of the specific heat and thermal expansion is revealed and their relation to the occupation number for the high-spin state of cobalt ions and to the insulator–metal transition is established. |
| Databáze: | OpenAIRE |
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