Oxidation behavior of amorphous metallic Ni3(SbTe3)2 compound

Amorphous Ni-3(SbTe3)(2) compound was prepared from a metathesis between Zintl phase K3SbTe3 and NiBr2 in solution and its oxidation behavior was investigated in the temperature range of 200-700 degrees C in air. To characterize the sample, thermogravimetry (TG), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis by X-ray (EDAX) analyses were performed and electrical conductivity was measured as a function of temperature in the range of 25-800 degrees C in air. The specimen showed a metallic conducting-like behavior below 585 degrees C while a semiconducting-like behavior above 585 degrees C. At a first oxidation step of Ni3(SbTe3)2 below 500 degrees C, TeO2 phase is formed. Above 500 degrees C, NiO phase is formed, then some NiO reacts with TeO2 to form NiTeO3 and NiSb2O6 is simultaneously formed. Above 700 degrees C, NiTeO3 is further reacted with TeO2 to form NiTe2O5. Both NiTeO3 and NiTe2O5 are decomposed above 774 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.