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 Gd2-xSrx/2Cex/2Zr2O7 (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.