Ion beam irradiation of lanthanum and thorium-doped yttrium titanates

Abstract Y 2 Ti 2 O 7 pyrochlores doped with La have been sintered at 1373 K for 12 h with the designed compositions of the (La x Y 1− x ) 2 Ti 2 O 7 system ( x = 0, 0.08, 0.5, and 1), and the phase compositions were analyzed by X-ray diffraction. Limited amounts of La were incorporated into yttrium titanate pyrochlore structure for La-doped samples; while, the end member composition of La 2 Ti 2 O 7 formed a layered perovskite structure. Ion beam-induced amorphization occurred for all compositions in the (La x Y 1− x ) 2 Ti 2 O 7 binary under 1 MeV Kr 2+ irradiation at room temperature, and the critical amorphization dose decreased with increasing amounts of La 3+ . The critical amorphization temperatures for Y 2 Ti 2 O 7 , (La 0.162 Y 0.838 ) 2 Ti 2 O 7 and La 2 Ti 2 O 7 were determined to be ∼780, 890 and 920 K, respectively. Th 4+ and Fe 3+ -doped yttrium titanate pyrochlores were synthesized at 1373 K by sintering Y 2 Ti 2 O 7 with (ThO 2 + Fe 2 O 3 ). Pyrochlore structures and the chemical compositions were primarily identified by the X-ray diffraction and energy dispersive X-ray (EDX) measurements. The lattice parameter and the critical amorphization dose (1 MeV Kr 2+ at room temperature) increase for yttrium titanate pyrochlores with the addition of Th. The increasing ‘resistance’ to amorphization with less La and greater Th and Fe contents for (Y 1− x La x ) 2 Ti 2 O 7 and Y 2 Ti 2 O 7 –Fe 2 O 3 –ThO 2 systems, respectively, are consistent with the changes in the average ionic radius ratio at the A-sites and B-sites. These results suggest that the addition of lanthanides and actinides (e.g., Th, U, or Pu) will affect the structural stability, as well as the radiation response behavior of the pyrochlore structure-type.