Produção e caracterização estrutural, térmica e óptica da liga semicondutora NiSb2

Abstract

A mixture of simple podwers of Ni and Sb with a nominal composition of Ni34Sb76 was submitted to mechanical milling, a process divided in six steps and followed by a X-ray diffraction (XDR) measurements. The duration of the milling was of 39 hours. A nucleation of a NiSb phase occurred, which holds a profound relevance in the cristalization of NiSb2. Its structural evolution was characterized by the following experimental techniques: X-ray diffraction (XRD) and Raman spectroscopy (ER). The structural parameters were refined by the Rietveldmethod (MR) using the GSAS package. A comparison between the results obtaind and the information present in the literature was done. A thermal treatment that lasted 9 hours was performed in the NbSb+Sb sample (obtained after 39 hours of milling on the original sample), with varying temperatures (25 ◦C, 100 ◦C, 200 ◦C and 300 ◦C), followed by X-ray diffraction measurements in sito by which a change in the sample structure was observed at 200 ◦C. At 300 ◦C it was observed in the XDR patterns the nucleation of NiSb2 and Sb2O3 phases. A Differential Scanning Calorimetry was (DSC) performed for confirmation of the XDR results. It was noted that NiSb2 nucleates at 263 oC, while Sb2O3 crystalised only at 309 oC. Measures of Raman espectroscopy were performed in various laser power levels, on the heat treated sample, were the vibrational modes of NiSb2 and NiSb were not found.