Influence of minor oxidation of the precursor powders to form nanocrystalline CdTe by mechanical alloying

Nanocrystalline CdTe was prepared by mechanical alloying using Te and Cd equiatomic powder mixture slightly oxidized due air exposition (6% α-TeO2 and 10% CdO, respectively). X-ray diffraction, energy dispersive spectroscopy, differential scanning calorimetry and Raman spectroscopy techniques were used to study the structural, chemical, thermal and optical properties of the milled powder. An annealing of the mechanical alloyed sample at 550 °C for 6 h was performed to clarify thermal reactions showed in the calorimetry measurement. The main crystalline phase formed was the zinc blende CdTe, but residual amorphous and minority crystalline Cd2(Te2O7) phases were also observed for mechanical alloyed and annealed samples, respectively. The structural parameters, phase fractions, mean crystallite sizes and strains of all crystalline phases were obtained from Rietveld analyses of the X-ray patterns. Raman results showed the disappearing of high-frequency modes of α-TeO2 after milling and suggest the photo-induced decomposition of CdTe phase and/or the recombination of Te atoms from the interfacial component to trigonal form for both samples.