Study of MgB2 phase formation by using XRD, SEM, thermal and magnetic measurements

MgB2 phase formation of samples with stoichiometric ratio of 1:2, prepared by sintering at different nine temperature values (500–900 °C) for 1 h were determined and examined by X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) methods. In order to support the results obtained from the above measurements and analyses the Mg:B (1:2) powder was subject to thermal studies. In conjunction with this, the thermal behaviors of the non-sintered powder samples were also studied their characteristics via thermal analysis techniques including Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) simultaneously. During the thermal analyses, Mg:B (1:2) powder was placed in an Al2O3 cup with a lid were investigated at different heating rates (5, 7.5, 10, and 15 °C/min) under high-purity Argon atmosphere. By analyzing the graphics gathered from the measurement results the effect of fundamental thermal events on MgB2 phase formation was deeply discussed by considering some data such as, crystallization, melting point, oxidation and evaporation, which can mainly be obtained from a usual thermal analysis technique. The peak temperatures of exothermic lines in DSC curves that indicate the formation of MgB2 were determined by derivative lines of the curves. With help of this information, the value of activation energy of MgB2 phase was found as EMgB2 = 219.9 kJ/mol by Kissinger Method. Moreover, in order to study the superconductivity of the samples; the sample sintered at 900 °C which was showing a considerable single phase property, was chosen for AC susceptibility measurement. For this sample, the onset temperature which is also called the transition temperature for superconductivity phase was found as Tc = 38.7 K.

► Activation energy EMgB2 was calculated from Kissinger formula.
► The single-step changes indicate the presence of a strong coupling between the grains of MgB2.
► The onset temperature which is also called the transition temperature for superconductivity phase was found as Tc = 38.7 K.
► Samples were produced by solid state reaction technique.