In situ TEM study of ion-beam-induced amorphization of complex silicate structures

In-situ TEM with ion irradiation was used to study the radiation- induced amorphization (metamictization) of naturally occurring silicates: neptunite [Na2KLi(Fe,Mn)2Ti2(SiO3)8], titanite (CaTiSiO5), gadolinite (REE2FeBe2Si2O10), zircon (ZrSiO4), and olivine [(Mg, Fe)2SiO4]. They were irradiated with 1.5 MeV Kr{sup +} ions the Argonne HVEM-Tandem Facility at room temperature with electron diffraction pattern monitored in situ. Critical doses required for amorphization of the electron transparent thickness of neptunite, titanite, gadolinite, zircon, and olivine are 1.7, 2.0, 2.3, 4.8, and 6.0x10{sup 14} ions/cm{sup 2}, respectively. Results show a correlation between amorphization dose and the chemical/structural complexity of these 5 minerals. The most complex, neptunite, becomes amorphous at the lowest critical dose. The critical amorphization dose also increases with the melting point