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The ternary material Mn2SiTe4 was synthesized by direct fusion using the annealing method. X-ray powder diffraction analysis indicated that this material crystallizes in the olivine-type structure, space group Pnma, Z = 4, with unit cell parameters: a = 13.905(2) Å, b = 8.128(1) Å, c = 6.526(1) Å, V = 737.6(2) Å3. This olivine structure can be described from a hexagonal close-packing of selenium atoms where manganese atoms occupy ½ of the octahedral sites while silicon atoms lay in ⅛ of the tetrahedra. The magnetic susceptibility curve indicate a possible antiferromagnetic behavior for this material. This compound is related to the ternary layered Mn3Si2Te6 recently studied as possible two-dimensional (2D) magnetic material. [ABSTRACT FROM AUTHOR]

A polycrystalline ingot (30mm long, 10mm diameter) of the alloy (CuInTe2)1-x(NbTe)x with x=0.5 has been produced using the melt and anneal technique and characterized by X-Ray Diffraction (XRD), Diferential Thermal Analysys (DTA) and Scanning Electron Microscopy (SEM). From XRD results, and using Rietveld refinement method, the crystal structure has been obtained indicating than this alloy crystallizes in a chalcopyrite-like structure, space group 𝑃𝑃42c (Nº 112), unit cell parameters a = 6.1933(2) Å, c = 12.4293(2) Å, V = 476.75(2) ų, figures of merit Re xp= 6.7%, Rp= 7.5%, Rwp= 7.3%, and S = 1.1. DTA measurements indicate three thermal transitions at 1028, 977 and 886 K in the heating cycle, and 1016, 900 and 848 K in the cooling. The transitions at 1028 and 1016 correspond to the melting and solidification point, respectively; the transitions at 977 and 900 K are of solid to liquid+solid type, whereas the transitions at 886 and 848 K correspond to order-disorder. The melting point is incongruent. In the diffraction pattern, traces of a secondary phase are observed; this phase has been identified using SEM technique as (CuIn)0.5NbTe2. [ABSTRACT FROM AUTHOR]

Background: Quaternary compounds bellowing to the I2-II-IV-VI4 system are of considerable technological interest due to their possible use in the preparation of solar cell and thermoelectric materials devices. In recent years, considerable attention has been focused on the detailed study of quaternary chalcogenide compounds related to the chalcopyrite compounds, particularly AgInSe2, which has emerged as a leading material for the preparation of photovoltaic devices due to their potential applications in solar cell technology. Aims: This work focuses on synthesis, chemical analysis, thermal study, magnetism measurement, and crystal structural characterization of the quaternary semiconductor Ag2FeGeSe4, an essential member of the family I2-II-IV-VI4. Methods: This material was synthesized by the melt and anneal technique. The chemical analysis was carried out by scanning electron microscopy (SEM) and differential thermal analysis (DTA). Magnetic susceptibility (χ) as a function of temperature and magnetization as a function of the magnetic field were also performed, and crystal structure analysis was made employing the Rietveld method with powder X-ray diffraction data. Results and Discussion: The preparation confirms the formation of the quaternary compound with stoichiometric 2:1:1:4 according to the chemical analysis. This quaternary compound melt at 1015 K, and show an antiferromagnetic behavior with Neel temperature TN of 240 K. The Debye temperature (θD) estimated for this compound was 194 K. The quaternary chalcogenide compound Ag2FeGeSe4 crystallizes in the orthorhombic space group Pmn21, Z = 4, with unit cell parameters: a = 7.6478(1) Å, b = 6.5071(1) Å, c = 6.4260(1) Å, and V = 319.79(1) ų, in a wurtzite-stannite arrangement with a Cu2CdGeS4-type structure, which is characterized by a three-dimensional arrangement of slightly distorted AgSe4, FeSe4, and GeSe4 tetrahedra connected by corners. In this structure, each Se atom is coordinated by four cations located at the corners of a slightly distorted tetrahedron, and each cation is tetrahedrally bonded to four anions. Conclusions: The melt and anneal method remains effective for preparing compounds chalcogenides as the quaternary Ag2FeGeSe4, a new member of I2-II-IV-VI4 family of semiconductors, which crystallizes in the non-centrosymmetric space group Pmn21 with diamond-like structure. The crystal structure information of this compound allows explaining their magnetic properties, which in combination with its semiconductor properties make this material a potential aspirant for different applications, mainly in solar cells. [ABSTRACT FROM AUTHOR]

The new (CuGa)0.52TaSe2 alloy was synthesized by the melt and annealing technique and studied by SEM, DTA, and XRPD techniques. Its structure has been refined by the Rietveld method using X-ray powder diffraction data. This compound crystallizes in the hexagonal space group P-6m2 (Nº 187) with unit cell parameters a = 3.648(2) Å, c = 13.568(4) Å, V = 156.4(1) Å3, Z = 2. The crystal structure is based on the MoS2-type of stacking of TaSe2 layers with a partial ordering of Cu and Ga cations over the tetrahedral sites. The powder pattern was composed of 63.9% of the principal phase (CuGa)0.52TaSe2 and 26.3% of CuGaSe2, 9.8% of TaSe3, as the secondary phases. [ABSTRACT FROM AUTHOR]