Effect of starting composition and annealing temperature on irreversibility field and critical current density in MgxB2

Investigation of effect of annealing temperature on mechanical properties of MgB2

“…These lattice parameters are reasonable consistent with other work [41]. The intensity of all peaks increases while the position of the peaks shifts towards smaller angles with increasing the annealing temperatures up to 850 • C then decreases at 950 • C. Increase of the intensity of the peaks and the decrease of the FWHM with increasing the annealing temper- The XRD pattern of M950 sample showed, besides MgB 2 , the presence of small amount of elemental B peaks [17,19]. It was observed that no traces of MgO or degradation compounds such as MgB 6 or MgB 12 .…”

“…In these investigations, variations in the lattice parameters, microstructure, critical transition temperature and critical current density values were observed with the chemical composition conditions. Variations in these values were also obtained with the preparation conditions [13][14][15][16][17][18][19][20]. In a previous study of the present samples, the influence of magnetic field on hysteretic ac losses in bulk MgB 2 was investigated by using Hall probe ac susceptibility [21].…”

Preparation and characterisation of Os doped MgB 2

“…The ion radius of Os 4+ is significantly lower than that of Mg 2+ (63 pm versus 72 pm in VI-fold coordination [37]) and this could explain the decrease of the a-axis lattice parameter up to a maximum solubility of about x = 0.015. As for the slight decrease of the c-axis parameter beyond x = 0.015, it could be an indirect consequence of the formation of an impurity phase containing Mg and/or B in an atomic ratio different from MgB 2 , possibly in association with Os, because this would lead to a change of the stoichiometry of the remaining MgB 2 matrix and it has been previously shown that modifications of the Mg:B ratio in MgB 2 results in subtle changes of the lattice parameters [38][39][40][41][42].…”

Phase 1 Final Technical Report - MgB2 Synthesis for High Field Performance

“…This inhomogeneity in the final product arises from either non-uniform mixing of the dopants or from the formation of non-superconducting parasitic phases like MgB 4 , MgB 7 , Mg 2 B 25 , etc. [1][2][3][4] which form because of incomplete reaction. One of the reasons for the latter is directly related to the fact that as compared to amorph- ous boron, the crystalline boron which is in most of the cases the β-rhombohedral phase has a lower reactivity and thus limits Mg diffusion.…”