Resumo

GRIMA-GALLARDO, Pedro et al. Preparation, crystal structure, thermal analysis, scanning electron microscopy and optical band-gaps of Cu₂GeTe₄ and Cu₂SnTe₄ alloys. Rev. LatinAm. Metal. Mater. [online]. 2015, vol.35, n.2, pp.259-268. ISSN 0255-6952.

Polycrystalline samples (weight ~ 1g) of Cu₂GeTe₄ and Cu₂SnTe₄ alloys were prepared by the usual melt and anneal method and the products characterized by X-Ray Diffraction (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM) and Optical Diffuse Reflectance UV/VIS/NIR Spectroscopy techniques. It was found that: a) Cu₂GeTe₄ and Cu₂SnTe₄ crystallize in an orthorhombic structure (s.g. Imm2; Nº 44) with lattice parameters a=5.9281(4) Å, b=4.2211(6) Å, c=12.645(5) Å and a=6.0375(6) Å, b= 4.2706 (3) Å, c=12.844(1) Å, respectively; b) both alloys show two thermal transitions: 762 and 636K upon heating and; 700 and 578K upon cooling for Cu₂GeTe₄; 702 and 636K upon heating and; 650 and 590K upon cooling for Cu₂SnTe₄; c) both alloys present large deviations of stoichiometry for the cations Cu (~35%), Ge (7.2%) and Sn (26.4%) and minor deviation within the experimental error, for the anion Te; and, d) the measured optical band gaps were 0.63 and 0.53 eV for Cu₂SnTe₄ and Cu₂GeTe₄, respectively.

Palavras-chave : Semiconductor alloys; X-Ray Diffraction; Differential Thermal Analysis (DTA); Scanning Electron Microscopy (SEM); Optical Diffuse Reflectance UV/VIS/NIR Spectroscopy; u₂GeTe₄; Cu₂SnTe₄.

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