Raman Study of Polycrystalline Si3N4 Irradiated with Swift Heavy Ions

Abstract

A depth-resolved Raman spectroscopy technique was used to study the residual stress profiles in polycrystalline silicon nitride that was irradiated with Xe (167 MeV, 1 × 1011 cm−2 ÷ 4.87 × 1013 cm−2) and Bi (710 MeV, 1 × 1011 cm−2 ÷ 1 × 1013 cm−2) ions. It was shown that both the compressive and tensile stress fields were formed in the irradiated specimen, separated by a buffer zone that was located at a depth that coincided with the thickness of layer, amorphized due to multiple overlapping track regions. The compressive stresses were registered in a subsurface region, while at a greater depth, the tensile stresses were recorded and their levels reached the maximum value at the end of ion range. The size of the amorphous layer was evaluated from the dose dependence of the full width at half maximum (FWHM) (FWHM of the dominant 204 cm−1 line in the Raman spectra and scanning electron microscopy.

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

“…In turn, the amorphization processes so evident for Si 3 N 4 ceramics were not experimentally detected for AlN and SiC ceramics. It is also worth noting that for Si 3 N 4 ceramics, intermittent latent tracks were found earlier in [ 32 , 33 , 34 ], the presence of which the authors attribute to the energy losses of the incident ions, as well as the destruction of chemical and crystalline bonds. However, it should be noted that the density of the detected tracks is much less than the irradiation fluence, which indicates that the latent discontinuous tracks are formed by a more complex mechanism in Si 3 N 4 ceramics than similar structural elements in dielectric polymers.…”

“…More intensive reductions in the strength characteristics for Si 3 N 4 ceramics at irradiation fluences higher than 5 × 10 13 ion/cm 2 can be caused by the amorphization processes of the damaged near-surface layer. More about the amorphization processes and increases in the degree of structural disorder in Si 3 N 4 ceramics under irradiation by heavy ions of Xe and Bi was reported in [ 32 , 33 , 34 ]. The authors, using Raman spectroscopy, showed that the so-called amorphization of the near-surface layer occurs when the fluence exceeds 10 13 ions/cm 2 depending on the type of incident ions.…”

Study of the Influence of the Irradiation Flux Density on the Formation of a Defect Structure in AlN in the Case of the Effect of Overlapping of the Heavy Ion Motion Trajectories in the Near-Surface Layer

“…Moreover, the emergence of residual mechanical stresses occurs because of the dominance of electronic ionization losses along the trajectory of ions in the material, leading to the formation of structurally changed areas in the damaged layer. It should also be noted that, in [44], a close to equiprobable distribution of residual mechanical stresses was shown almost along the entire ion motion trajectory, which, in turn, may indicate an isotropic change in material properties. At the same time, the observed anisotropic distortions of the shape and intensity of diffraction reflections during shooting in the geometry ϕ = 0-360 • , considering the foregoing, can be attributable to the effects of overlapping structurally changed areas in the damaged layer.…”

“…In some cases, such effects are associated with the appearance of texture effects [42,43] under external mechanical influences. In the case of irradiation, as was shown in [44], the effects caused by irradiation with heavy ions are comparable to the effects of mechanical residual stresses in the damaged layer, the accumulation of which can lead to a destructive change in the properties of ceramics. Moreover, the emergence of residual mechanical stresses occurs because of the dominance of electronic ionization losses along the trajectory of ions in the material, leading to the formation of structurally changed areas in the damaged layer.…”

Study of Radiation Damage Kinetics in Dispersed Nuclear Fuel on Zirconium Dioxide Doped with Cerium Dioxide

“…These are high-precision, non-destructive control methods that make it possible to determine the kinetics of accumulation of radiation damage with high accuracy as well as establishing the main causes associated with deformation distortions of the structure [34,35]. Thus, in a number of works [36,37] using high-resolution electron microscopy, the results of the relationship between the latent tracks formed as a result of irradiation, mechanical residual stresses, structural changes and amorphization processes were obtained. Using the X-ray diffraction analysis aimed at assessing alterations in structural parameters and their distortion, dose dependences of the crystal lattice swelling and its deformation as a function of the irradiation fluence were obtained in a number of works [38,39].…”