The incorporation of plutonium in lanthanum zirconate pyrochlore

Abstract The incorporation of plutonium (Pu) within lanthanum zirconate pyrochlore was investigated using air, argon, and N 2 –3.5%H 2 sintering atmospheres together with Ca 2+ and Sr 2+ incorporation for charge compensation. The samples have been characterised in the first instance by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy (DRS). The results show Pu can be exchanged for La 3+ on the A-site with and without charge compensation and for Zr 4+ on the B-site. DRS measurements were made over the wavenumber range of 4000–19,000 cm −1 and the Pu in all air- and argon-sintered samples was found to be present as Pu 4+ while that in samples sintered in N 2 –3.5%H 2 was present as Pu 3+ . The Pu valence was confirmed for three of the samples using X-ray near-edge absorption spectroscopy (XANES). Pu valences >4+ were not observed in any of the samples.