Alpha-decay damage in murataite-based ceramics

Samples of murataite ceramics with the composition (wt.%) 3.8 Al2O3, 10.5 CaO, 54.0 TiO2, 10.6 MnO, 6.0 Fe2O3, 4.6 ZrO2, 8.1 ThO2, 2.4 Cm2O3 (1.8 244Cm) and a specific activity of 5.5x1010 Bq/g were prepared by cold pressing and sintering at 1250 deg. C for 24 hrs or by melting and recrystallisation in a resistive furnace at 1325 deg. C and 1350 deg. C for 1 hr. In the sintered ceramics murataite polytypes with five-fold (5C) or three-fold (3C) repeats of the fluorite unit cell and crichtonite were found to be the major phases. Perovskite, pseudobrookite, and pyrochlore were observed as minor phases. The 5C polytype was rendered X-ray amorphous at a cumulative dose of 2.73x1018 α-decays/g (0.21 dpa) whilst the 3C polytype, which contained only traces of Cm, remains crystalline at this dose. In the melted ceramics the 5C and 8C murataite polytypes were found to be the major phases (80-90 % of the bulk) and minor amounts of rutile, crichtonite and perovskite were also observed. Complete amorphization of the murataite polytypes in the ceramics melted at 1325 and 13500 C was achieved at doses of 2.46x1018 α-decays/g (0.19 dpa) and 2.53x1018 α-decays/g (0.20 dpa), respectively. (authors)