Влияние допирования титаном и диоксидом титана на фазовый состав, структуру и транспортные свойства халькогенидов железа
Аннотация
The master’s dissertation consists of an introduction, a literature review, a description of experimental techniques, a statement of the purpose and objectives of the study, results and discussion, a conclusion, a list references used, which includes 40 items. The content of the work is presented on 86 pages, including 64 figures and 12 tables.
Currently, several groups of iron-containing superconductors are known, but the most promising in terms of research and understanding of the nature of the superconducting properties in this class of materials is the FeSe compound due to its simple structure and the absence of such toxic elements as arsenic. The critical temperature of the superconducting transition Tc in FeSe is only 8 K, but there are ways to increase it to values about 100 K. One of the simplest ways to influence the superconducting properties is to replace iron and/or selenium atoms with atoms of other elements. Thus, for samples of the composition FeSe0.5Te0.5, the temperature of the superconducting transition is Tc ~ 15 K.
The purpose of this study was to establish the role of changes in the chemical composition and phase ratio when titanium and titanium dioxide doping on the formation of the superconducting properties of iron chalcogenides with a composition close to equiatomic.
The compounds were synthesized by the method of solid-phase reactions in evacuated quartz tubes. Coarse-grained samples were obtained by remelting in a vertical gradient furnace. X-ray diffraction analysis was performed on a Bruker AXS D8 ADVANCE diffractometer with subsequent processing of the results using the FullProf software package. The electrical resistance was measured by a four-contact method using a CryoFree 204 refrigerator in the temperature range 5-350 K. The field and temperature dependences of magnetization of the samples were measured on a SQUID magnetometer MPMS-XL7 EC (Quantum Design) in the temperature range 2-300 K and in magnetic fields up to 70 kOe.
The paper presents the results of a study of the effect of titanium and titanium dioxide doping on the crystal structure, phase composition and superconducting properties of samples based on Fe1.02Se, Fe1.02S and Fe1.02Se0.5Te0.5. Based on X-ray diffraction studies, measurements of the temperature dependences of the electrical resistivity and field dependences of the magnetization, it has been shown that the addition of titanium and titanium dioxide has a different effect on the phase composition and superconducting characteristics of materials. The regions of existence of the superconducting tetragonal phase are determined. The critical current density was estimated from the magnetization data. The conclusion is made about the possibility of improving the superconducting characteristics for a number of materials studied by doping.
The results of the work were presented at 14 national and international conferences.
This work was financially supported by the Ministry of Education and Science of the Russian Federation (project No. 3.2916.2017/4.6).
Currently, several groups of iron-containing superconductors are known, but the most promising in terms of research and understanding of the nature of the superconducting properties in this class of materials is the FeSe compound due to its simple structure and the absence of such toxic elements as arsenic. The critical temperature of the superconducting transition Tc in FeSe is only 8 K, but there are ways to increase it to values about 100 K. One of the simplest ways to influence the superconducting properties is to replace iron and/or selenium atoms with atoms of other elements. Thus, for samples of the composition FeSe0.5Te0.5, the temperature of the superconducting transition is Tc ~ 15 K.
The purpose of this study was to establish the role of changes in the chemical composition and phase ratio when titanium and titanium dioxide doping on the formation of the superconducting properties of iron chalcogenides with a composition close to equiatomic.
The compounds were synthesized by the method of solid-phase reactions in evacuated quartz tubes. Coarse-grained samples were obtained by remelting in a vertical gradient furnace. X-ray diffraction analysis was performed on a Bruker AXS D8 ADVANCE diffractometer with subsequent processing of the results using the FullProf software package. The electrical resistance was measured by a four-contact method using a CryoFree 204 refrigerator in the temperature range 5-350 K. The field and temperature dependences of magnetization of the samples were measured on a SQUID magnetometer MPMS-XL7 EC (Quantum Design) in the temperature range 2-300 K and in magnetic fields up to 70 kOe.
The paper presents the results of a study of the effect of titanium and titanium dioxide doping on the crystal structure, phase composition and superconducting properties of samples based on Fe1.02Se, Fe1.02S and Fe1.02Se0.5Te0.5. Based on X-ray diffraction studies, measurements of the temperature dependences of the electrical resistivity and field dependences of the magnetization, it has been shown that the addition of titanium and titanium dioxide has a different effect on the phase composition and superconducting characteristics of materials. The regions of existence of the superconducting tetragonal phase are determined. The critical current density was estimated from the magnetization data. The conclusion is made about the possibility of improving the superconducting characteristics for a number of materials studied by doping.
The results of the work were presented at 14 national and international conferences.
This work was financially supported by the Ministry of Education and Science of the Russian Federation (project No. 3.2916.2017/4.6).