Synthesis of yttrium titanate stannate (Y2Ti2?xSnxO7, x = 0–2) pyrochlore glass–ceramics as potential nuclear waste form

Y₂Ti_2?xSn_xO₇ (x = 0–2) pyrochlore sodium aluminoborosilicate glass–ceramics (GCs) are produced by calcining the pelletized Y–Ti–Sn oxide mixture and glass precursor at 1200 or 1300°C for 4 h. The metal oxide mixture is prepared by a soft chemistry route. X-ray diffraction, Raman spectroscopy, and electron microscopy are employed to investigate the formation of pyrochlore GCs and local crystal structures. Near phase pure Ti-rich pyrochlores are produced with minor phase SnO₂ observed for Sn-rich materials. The cell parameters of the pyrochlore structures refined by Le Bail fitting are in good agreement with the published data and increase linearly with the gradual increment of Sn substitution. With progressively increasing Sn proportion on pyrochlore B-site, Raman characteristic bands of the pyrochlore structure become sharper and well defined. The Raman A_1g peak position and its full width at half-maximum are linearly progressed with increasing x (Sn). The presence of the melting glass facilitates the pyrochlore formation, with ceramic grain sizes ranging from submicron to microns. Transmission electron microscopy and selected area electron diffraction observations indicate the sample possesses a relatively high crystallographic perfection at the atomic level. This new series of pyrochlore GCs and the method disclosed herein may pave the way for further materials development as potential nuclear waste forms.