Contribution of the Rietveld method to non-stoichiometric phase modeling. Part II: α-Tl5Te3 and μ Nb-Ni as experimental examples

Two detailed examples are considered to show the ability of powder diffraction data analyzed with the Rietveld method to get insight into the detailed structure of non-stoichiometric phases. Both the γ-phase in Tl-Te system and μ-phase in Nb-Ni system were investigated as a function of composition across their whole homogeneity domain. In the case of the γ Tl-Te phase, the excess Tl relative to the stoichiometric composition is accommodated by Tl substitution on one of the two Te sites. In the μ Nb-Ni, three of the five sites of the structure are partially disordered for all the compositions studied. The results are analyzed in view of Calphad modeling of both phases.