Experimentally and Theoretically Revealing the Co-Doping Effects of Ce-Sr in Gd₂Zr₂O₇

To safely dispose radioactive waste (including, e.g., thorium and radiostrontium), Ce⁴⁺ and Sr²⁺ were chosen as simulated surrogates of α and β waste and were introduced into the Gd³⁺ site in Gd₂Zr₂O₇ to maintain the average cationic radius and to compensate for charge. A series of Gd_2-SrCeZr₂O₇ (0.00 ≤ x ≤ 0.25) compounds were examined by experimental and theoretical calculations to investigate the co-doping effects of α and β waste in a Gd₂Zr₂O₇-based matrix. The effects of Ce⁴⁺ and Sr²⁺ content on the phase, unit cell parameters, active modes, mechanical property, and microstructure were studied systematically. Moreover, the limit of incorporation of Ce⁴⁺ and Sr²⁺ in Gd₂Zr₂O₇ pyrochlore and the lattice parameters were also calculated through virtual crystal approximation theory, and the results were found to well agree with experimental results.