Preparation of Composite Materials in the System Sb2Se3- Cu2Cr4Te7

It is known that chalcogenides of the main elements of subgroup V and ternary compounds and solid solutions based on them are widely used in optical devices in microelectronics as materials with high photosensitivity and thermoelectric properties. As2X3 → Sb2X3 → Bi2X3 are chalcogenide compounds, sulfur and selenide compounds being photosensitive [1-4], and telluride compounds increase thermoelectric properties [5,6]. In the interaction of copper and chromium chalcogenides, the obtained compounds CuCr2Se4, CuCr2Te4, Cu2Cr4Te7 are ferromagnetic semiconductor materials [7,8]. By chemical interaction between the lightsensitive compound Sb2Se3 and the ferromagnetic compound Cu2Cr4Te7, magneto-optical composite materials can be obtained that retain the properties of both components. Based on this, the study of the interaction between Sb2Se3 and Cu2Cr4Te7 compounds is of scientific and practical importance. The aim of this work is to obtain magneto-optical composite materials in the Sb2Se3-Cu2Cr4Te7 system, as well as to search for the region of solid solutions. The Sb2Se3 compound is obtained with open maxima and melts congruently at 890К, crystallizes in an orthorhombic system with lattice parameters: a=11.633; b=11.780; c=3.985Å, sp.gr. Pbnm- D2h 16, density ρ=5.843g/cm3 and microhardness Hμ=1200MPa [9]. The Cu2Cr4Te7 compound melts incongruently at 1273К and there is a large homogeneity region near it [10].

The synthesis of alloys of the Sb2Se3-Cu2Cr4Te7 system was carried out both from binary compounds and from elementary components by the method of direct ampoule melting in evacuated quartz ampoules. The alloys obtained were subjected to homogenizing annealing at 723K for 350h. Equilibrium alloys of the system were investigated by Differential Thermal (DTA), X-Ray Diffraction (XRD), Microstructural Analysis (MSA) and density determination and microhardness measurements. DTA was performed on an NTR-73 pyrometer using a combined Pt-Pt/Rh thermocouple. X-ray phase analysis was performed by recording a diffractograms on a D2 phaser. Microstructural studies were carried out using an MIM-8 metallographic microscope. Microhardness was measured on a PMT-3 device. To measure the magnetic susceptibility of the samples, they were carried out in the temperature range 150-600K on a magnetic balance with electromagnetic compensation. To measure the magnetization of the synthesized samples, a Voner-type vibration magnetometer was used [9,10].

To study the Sb2Se3-Cu2Cr4Te7 system, samples were synthesized in a wide range of concentrations, each 5-10mol%. Cooling of alloys that were carried out with the furnace turned on. The alloys are obtained in a compact form. Their color changes from gray to brilliant gray. DTA of alloys of the Sb2Se3-Cu2Cr4Te7 system show that there are three effects on the thermograms of almost all alloys. In the area of 0-20mol.% Cu2Cr4Te7, two heating effects are obtained. The study of the microstructure of the annealed samples showed that single-phase alloys exist only near the initial components. The rest of the alloys in the system are two-phase. In order to refine the results of DTA and MSA, X-ray phase analysis was performed. For alloys containing 4,20,70 and 85mol.% Cu2Cr4Te7, X-ray diffraction patterns were taken. XRD of the annealed alloys of the Sb2Se3- Cu2Cr4Te7 system showed that the diffraction patterns of cast alloys of 20 and 70mol% Cu2Cr4Te7, intense diffraction lines are observed, which consist of the diffraction line of the initial components. This means that these samples are two-phase alloys. Diffraction lines of the sample 4mol.% Cu2Cr4Te7 do not differ from the diffraction lines of the Sb2Se3 compound, only differ in interplanar distances. This composition belongs to the field of solid solutions based on Sb2Se3, and the sample is 15mol% Sb2Se3 also belong to the region of solid solutions based on Cu2Cr4Te7. To study the magnetizing ability of solid solution alloys in the temperature range 11270- 1370K, samples 2,3 and 5mol% Sb2Se3 were synthesized. The alloys were heat treated at 773K for 100 hours for homogenization. The magnetization of samples 2,3 and 5mol.% Sb2Se3 was carried out in the temperature range 150-600K. Even in the absence of an external magnetic field, substances with strong magnetization are called ferrimagnets. A decrease in magnetization is observed depending on the temperature and composition. For samples containing 2,3 and 5mol% Sb2Se3, the Curie temperature in a very weak magnetic field of 1.0 Erst was 280 and 330K. The magnetic permeability is measured in a magnetic field H=10k Erst. The value of the molar susceptibility of the samples was determined by the formula χ=χ0. (m0/m)(i/i0) M where χ0- is the specific magnetic susceptibility of the standard (Mohr’s salt), m0 and m are the mass of the standard and the sample, M is the molecular weight of the sample.

Chemical interactions in the Sb2Se3-Cu2Cr4Te7 system were studied by methods of physicochemical analysis (DTA, XRD, MSA, as well as density determination and microhardness measurements). DTA of the samples showed that there are two and three endothermic effects on the thermograms. It is revealed that the phase diagram of the Sb2Se3-Cu2Cr4Te7 system is purely quasi-binary. In the system, solid solutions based on Sb2Se3 reach 4mol%, and based on Cu2Cr4Te7 - upto -15mol%. The magnetization and permeability of (Cu2Cr4Te7)1-x (Sb2Se3)x solid solutions were measured depending on the composition and temperature.

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