Influence of irradiation spectrum and implanted ions on the amorphization of ceramics

Abstract

Polycrystalline specimens of alumina (Al2O3), magnesium aluminate spinel (MgA1204), magnesia (MgO), silicon nitride (Si3N4) and silicon carbide (Sic) were irradiated with various ions at temperatures between 200 K and 450 K, and the microstructures were examined following irradiation using cross-section transmission electron microscopy. Amorphization was not observed in any of the irradiated oxide ceramics, despite damage energy densities up to-7 keV/atom (-70 displacements per atom). On the other hand, Sic readily amorphized after damage levels of-0.4 dpa at room temperature. Silicon nitride exhibited intemediate behavior;. irradiation with Fe* ions at room temperatm produced amorphization in the implanted ion region after damage levels of-1 dpa. However, irradiated regions outside of the implanted ion region did not amorphize even after damage levels in excess of 5 dpa. The amorphous layer in the Fe-implanted region of Si3N4 did not appear if the specimen was simultaneously irradiated with 1 MeV He+ ions at room temperature. By comparison with published results, it is concluded that the implantation of certain chemical species has a pronounced effect on the amorphizahon threshold dose of all five materials. Intense ionizing d a t i o n inhibits amorpkation in Si3N4, but does not appear to signtficantly influence the amorphimion behavior of Sic.

Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu− ions

“…Maximum values of Al and O damage peaks appeared at a flux of 1.9 · 10 17 ions/m 2 s. RBS/ channeling measurements indicated that spinel was not completely amorphized over the flux range examined, although the crystalline lattice is significantly damaged. This result agrees with several studies of spinel irradiated with lower flux at room temperature [24,25]. The resistance of spinel against amorphization at high-flux may also arise from the recombination of radiation-induced interstitials with structural vacancies in the spinel structure.…”

Irradiation effects induced in silicon carbide by low and high energy ions

“…In order to implement the ion-implantation based doping process for silicon carbide, previous works [1][2][3][4]10] mainly concentrated on the irradiation with ions of medium mass having energies of a few hundreds keV, i.e. in a slowing down regime where the nuclear energy loss is dominant.…”

“…It is worth mentioning that several review papers were published in the 90's [1][2][3][4] on ion implantation effects and ion beam processing of SiC at low energy. These investigations mainly deal with defect formation [5], amorphization and annealing [1], recrystallization [6,7] and electrical activation of dopant atoms [8].…”

Thermal conductivity degradation of ceramic materials due to low temperature, low dose neutron irradiation

“…Electron irradiation studies were not included in the estimation of the critical interstitial migration temperature, due to possibly large effects of ionization-induced diffusion [41]. To the authors knowledge there are no data from which the critical temperature for interstitial migration in silicon nitride can be accurately determined, though it can be inferred to be <80 K based on the resistance of Si 3 N 4 to ion beam-induced amorphization at 80 K up to a dose level of 30 dpa [74].…”