Abstract
Amorphizable ceramics (LiNbO3, ZrSiO4, and Gd3Ga5O12) were irradiated with 200 MeV Au ions at an oblique incidence angle, and the as-irradiated samples were observed by transmission electron microscopy (TEM). Ion tracks in amorphizable ceramics are confirmed to be homogenous along the ion paths. Magnified TEM images show the formation of bell-shaped hillocks. The ion track diameter and hillock diameter are similar for all the amorphizable ceramics, while there is a tendency for the hillocks to be slightly bigger than the ion tracks. For SrTiO3 (STO) and 0.5 wt% niobium-doped STO (Nb-STO), whose hillock formation has not been fully explored, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO. The material dependence of the nanostructure formation is explained in terms of the intricate recrystallization process.
Highlights
Long nanometer-sized damage trails are created in ceramics continuously along the trajectories of swift heavy ions (SHIs), if the energy transfer from a SHI to an electron system of ceramics is sufficiently high [1,2,3]
According to our previous study [36], most of the crystalline hillocks in these fluorides are nearly semispherical, some of the hillocks have nearly spherical AosisnbhhusaateiphporAeeevn.meosflSdfuaoinhtobrcaiprylenilhdoTrioceezEbkcsaMrlsbsiyqhla.seunoTtaceduhlellienridnzaiocaombnitndei-iosectspnnsriamhcpsceeulkiralaciayahncrsnagatladlosesn.hhLtiLhiamilNpialnoptebecoocO-krlfati3dnakC,nieZebatOhmerrSoo2eeimlxOt(eeFpo4iril,ngsgaaeiubannnorrdeeeetdhosG8uibflamdsy)u3.iioGtolTharnairhed5tOefderoas1dir2ffcaikaweffnlsredleeartrnCenhecnedeeicOrabeirnm2aeb,ldvotle-hiortasweplhtuehfaemodipezrneemwadbotiahltfhteheipiolc2rslneoo0prcpt0harkrmueMosrsciaiiececorVssaen,sl. the hillock diameter is found to be slightly larger than the ion track diameter
The transmission electron microscopy (TEM) images of ion tracks in STO and niobium-doped STO (Nb-STO) irradiated with 200 MeV Au show similar features to those observed in the non-amorphizable ceramics
Summary
Long nanometer-sized damage trails are created in ceramics continuously along the trajectories of swift heavy ions (SHIs), if the energy transfer from a SHI to an electron system of ceramics is sufficiently high [1,2,3]. Our recent studies revealed that both ion tracks and hillocks are amorphous in the case of amorphizable ceramics (Y3Fe5O12 (YIG)) [36,37], whereas crystalline hillocks are found in the case of non-amorphizable ceramics (CaF2, SrF2, BaF2, and CeO2) [36,38]. It was found that the hillock diameter always coincides with the diameter of a melt predicted by the thermal spike model for both amorphizable and non-amorphizable ceramics. This means that a hillock diameter value is affected by a melting process, but it remains unchanged after the subsequent recrystallization process. Based on the TEM investigations of both amorphizable and non-amorphizable ceramics, we discuss how the SHI-induced nanostructure formation depends on the intricate recrystallization process
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