Investigation of the lattice parameter and sintering characteristics of uranium dioxide doped with zirconium and gadolinia

The lattice parameters and sintering characteristics of zirconia (ZrO2) and gadolinia (Gd2O3) doped uranium dioxide (UO2) have been thoroughly examined. The sintering behavior and lattice parameter of UO2 were both influenced when those dopants were added. The effects were dependable on the concentration of the respective dopants which have a different valence state. In the UO2 matrix, zirconium was present as Zr4+ ions and gadolinium as Gd3+ ions. Uranium dioxide (or urania) powder was homogeneously mixed with the zirconia or gadolinia powders by means of a dry mechanical milling. Subsequently, the mixed powders were pelletized and sintered for 4 hours into dense, solid pellets under reducing atmospheres at either 1680 or 1700 °C. By varying the atmosphere and dopant content, the stoichiometry of the end-product could be modified. The determination of the lattice parameter of the crystal microstructure was achieved through X-ray diffraction (XRD). The sintering behavior of the ceramic fuel was studied by dilatometry. The stoichiometry of produced samples was measured via thermogravimetric analysis. In accordance with literature, the lattice parameter decreased linearly for increasing dopant contents. The densification properties of the powder compacts were also significantly influenced by the addition of dopants.