Calorimetric studies of chalcogenide glasses, (Se65T35)(100-x)Sb-x, obtained by ice-water quenching, were performed by a non-isothermal method. An X-ray diffraction study, as a function of temperature, was carried out, with samples of different compositions. The activation energy for relaxation time, was determined from the heating-rate dependence of values of the glass transition temperature, as a function of x. A maximum in Delta E(t) versus antimony concentration occurs at 1-2 at%. Sb-121 Mossbauer results confirm the formation of Sb2Se3, by crystallization.