Pyrochlore Gd2Zr2O7 are considered as an excellent candidate for treatment of radioactive waste forms, because of its superior physical, chemical and anti-irradiation properties. To investigate the phase and structure of pyrochlore Gd2Zr2O7 used for immobilizing Pu （Ⅲ）, trivalent europium was used as the simulacrum for plutonium with trivalence. The compounds of stoichiometry Gd2-xEuxZr2O7（0.0≤x≤ 2.0） synthesized by high temperature solid state reaction method, were analyzed with the help of XRD and Rietveld structural refinement method. The results indicated that the phases of compounds continuously kept the phase of pyrochlore under our experimental condition. The linear relation between a and x was discovered in the system of Gd2-xEuxZr2O7（0.0≤x≤ 2.0） at 1 773 K, which accorded with a = 10.538 41 ＋ 0.008 95 x, V = 1 170.373 32 ＋ 2.985 97 x.
The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_xO_7 （0.0≤x≤2.0） were synthesized via a high temperature solid reaction method with Gd_2O_3 and ZrO_2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 ＋ 0.00825 x （0.2≤x≤2.0）, while V= 0.14668 ＋ 0.00711 x （0.2≤x≤2.0） was also achieved.
