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Structural, thermal and optical properties of Ag(In1-xGax)5Te8

Larissa T.Dur�?�?�?�?�?�?�?¡n, Josefa Est�?�?�?�?�?�?�?©vez Medina, Jaime A.Castro, Jos�?�?�?�?�?�?�?© R.Ferm�?�?�?�?�?�?�?­n, Ricardo J.Morales, Carlos A.Durante Rinc�?�?�?�?�?�?�?³n

Ingots of theAg(In1-xGax)5Te8 (0ï‚£xï‚£1) systemwere prepared by direct fusion of the stoichiometricmixture of the elements in evacuated quartz ampoules. The analysis of the X-ray powder diffraction data showed the presence of a single phase with tetragonal structure at room temperature for all the studied compositions. The lattice parameters a and c were calculated. Melting temperatures, from696 ºC for AgIn5Te8 to 775 ºC for AgGa5Te8,were obtained from Differential Thermal Analysis measurements performed on samples in evacuated quartz ampoules. Reflectance measurements were used to calculate the band gap energies and the real refraction indices. A direct band gap, slightly varying from1.34 to 1.39 eV (0ï‚£xï‚£0.4), was found in In-rich compounds, while an indirect band gap was found in all the studied compositions varying from1.11 to 1.14 eV (0ï‚£xï‚£1).