Phase diagram and local structure of Gd2(Zr1-xTix)2O7 and (Gd1-yNdy)2(Zr1-zCez)2O7 pyrochlore matrices for nuclear waste disposal

Aim of this proposal is to to map the crystallographic structure at different scale lengths of the following pyrochlore systems: A) Gd2(Zr1-xTix)2O7 solid solutions, which are promising compositions as matrices for the immobilization of actinides, and B) single and double doped (Gd1-yNdy)2(Zr1-zCez)2O7 compounds, to simulate the actinides immobilization (Nd3+ and Ce4+ are used as surrogates for incorporated Am3+ and Pu4+, respectively). To this purpose, high-resolution diffraction data will be analyzed using both the Rietveld method and the pair distribution function (PDF) analysis. The final goal is to map exhaustively the disorder introduced by doping (that is varying x, y and z in the compounds formula) paving the way to the use of these pyrochlore materials for actinides immobilization.