Comprehensive Understanding of Hillocks and Ion Tracks in Ceramics Irradiated with Swift Heavy Ions

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.

Thermal Spike Responses and Structure Evolutions in Lithium Niobate on Insulator (LNOI) under Swift Ion Irradiation

“…Obviously, the iTS calculations are consistent with TEM observations (Figure 2a,b). (ii) Recrystallization effect-comparing 0.80 MeV/u Cl ion irradiation with an E ele of 5.0 keV/nm and 0.70 MeV/u Ar ion irradiation with an E ele of 5.4 keV/nm, the energy deposition to the atoms of amorphous SiO 2 increases from 0.55 eV/atom to 0.60 eV/atom, and the corresponding atomic temperature increases from 2724 K to 3004 K. Thus, this effects leads to the transition from a completely amorphous state to a partially crystalline state at the melting region, similar to [30][31][32], demonstrating the appearance of the cylindrical recrystallization track in Figure 2d. For the Si substrate (Figure 4e,f), the atomic temperatures (715 K and 740 K) in the irradiation regions are significantly lower than the melting point T m (1420 K), and the irradiation energy deposited to atoms is lower than the critical threshold for damage production originating from the thermal spike process.…”

High-Energy Heavy Ion Irradiation of Al2O3, MgO and CaF2

“…Ion irradiation parameters such as ion type, energy and fluence can be easily tuned to achieve the desired densities of defects at pre-defined depths [ 1 , 2 , 3 ]. Furthermore, high-energy heavy ion irradiation can also be used, with a great degree of control, to change material surfaces [ 4 , 5 , 6 ] and create nanomaterials [ 7 , 8 , 9 , 10 , 11 ]. These attractive possibilities stem from the fact that high-energy heavy ions travel through the material in almost straight lines.…”

Study of Degradation Mechanisms of Strength and Thermal-Physical Properties of Nitride and Carbide Ceramics—Promising Materials for Nuclear Energy

“…Meanwhile, the increase in the coolant temperature, as well as the core operating temperature, requires the use of new types of reactor materials that have high melting temperatures (above 2000 °C), as well as good indicators of resistance to external influences, including mechanical and radiation damage [ 5 , 6 , 7 , 8 ]. There are also additional requirements for these materials used as structural materials, concerning safety and resistance to radiation defects and subsequent effects associated with their accumulation in the damaged layer exposed to irradiation, which can be several tens of microns thick [ 9 , 10 , 11 ]. The main effects caused by irradiation usually consist in the destruction of crystalline and chemical bonds, as well as disordering, amorphization, or swelling processes [ 12 , 13 , 14 , 15 ].…”