Thermophysical Properties of Rare-Earth-Stabilized Zirconia and Zirconate Pyrochlores as Surrogates for Actinide-Doped Zirconia

Thermophysical properties of rare-earth-stabilized zirconia and zirconate pyrochlores,A2Zr2O7 (A=La, Nd, Sm, Gd,Dy, Y),were evaluated by X-ray diffractometry, Raman spectroscopy, and the ultrasound pulse-echo method. Crystallographic analyses elucidated that La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, and Gd2Zr2O7 had the pyrochlore structure, whereas Dy2Zr2O7 and Y2Zr2O7 had the defect fluorite structure. For lanthanide pyrochlores, the thermal expansion became smaller with increasing ionic radius of A and increasing crystal binding energy. The elastic moduli and Debye temperature evaluated using longitudinal and transverse sound velocities also depend on the ionic radius and binding energy, and hence these values related to mechanical properties increase with the ionic radius of A. On the other hand, Poisson’s ratio was almost comparable among these pyrochlores. In addition, thermophysical properties of actinide pyrochlore are discussed in this study