ION-BEAM-INDUCED AMORPHIZATION OF LAPO4 AND SCPO4

LaPO4 and ScPO4 were irradiated by a 1.5 MeV Kr+ ion beam using the HV EM-tandem Facility at Argonne National Laboratory. The ion-beam-induce d amorphization was investigated over a temperature range of 20 to 570 K and the degree of amorphization was determined in-situ by monitorin g the gradual loss of electron diffraction maxima, Subsequent high-res olution TEM analysis revealed the development of an amorphous phase. L aPO4 and ScPO4 were found to have activation energies for irradiation- enhanced annealing of 0.02 and 0.11 eV, attributed to diffusion-driven epitaxial recrystallization. The critical temperatures of amorphizati on were found to be 365 and 540 K, respectively. Both materials recrys tallized under electron irradiation. These results suggest that the ph osphates are generally less sensitive to ion-beam irradiation over a w ide temperature range than are their silicate structure analogues and that the zircon structure-type has a higher energy barrier to recrysta llization than the related monazite structure-type.