Synthesis and microstructure of Gd2O3-doped HfO2 ceramics

The effect of Gd2O3-doping on the crystal structure, surface morphology and chemical composition of the Gd2O3–HfO2 system is reported. Gd2O3–HfO2 ceramics with variable composition were prepared by varying the Gd2O3 composition in the range of 0–38 mol% balanced HfO2. X-ray diffraction (XRD) analysis indicates that the Gd2O3 concentration influences the crystal structure of the Gd2O3–HfO2 ceramics. Pure HfO2 and Gd2O3 crystallize in monoclinic and body centered cubic structure, respectively. The Gd2O3–HfO2 ceramics exhibit mixed monoclinic and fluorite structure when the Gd2O3 concentration is varied from 4 to 12 mol%. At 20 mol% of Gd2O3, existence of only the fluorite phase was found. Increasing the Gd2O3 concentration to 38 mol% results in the formation of single-phase pyrochlore Gd2Hf2O7 (a = 5.258 Å).