Vol. 136 (2019) ACTA PHYSICA POLONICA A No. 2 Proceedings of the 12th International Conference “Ion Implantation and Other Applications of Ions and Electrons”, ION 2018 Microstructural Effects of Al Doping on Si 3 N 4 Irradiated with Swift Heavy Ions A. Janse van Vuuren a, * , V. Skuratov b , A. Ibrayeva c and M. Zdorovets c a Centre for HRTEM, Nelson Mandela University, University Way, Summerstrand, Port Elizabeth, 6031, South Africa b Flerov Laboratory for Nuclear Research, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, 141980, Moscow region, Russia c The Institute of Nuclear Physics, 1 Ibragimova Str., Almaty, 050032, Republic of Kazakhstan Transmission electron microscopy techniques were used to investigate the effect of swift xenon ions on the mi- crostructure of polycrystalline Al doped β -Si3N4. The target material was irradiated with Xe with energies between 167 and 220 MeV with initial stopping powers of 20 and 22 keV/nm, respectively. The fluences ranged between 3 × 10 11 to 6 × 10 14 cm -2 and irradiation was done at room temperature. The formation of discon- tinuous latent ion tracks was observed in all samples. The threshold stopping power for track formation in Al doped β -Si3N4 was determined to be approximately 8.9 keV/nm and the threshold fluence for amorphisation due to electronic stopping in the range between 1 × 10 13 and 2 × 10 14 cm -2 at a threshold stopping power of between 6.8 and 8.1 keV/nm. It was also found that the doping of β -Si3N4 with Al lowers the threshold for amorphisation as compared to pure β -Si3N4. DOI: 10.12693/APhysPolA.136.241 PACS/topics: 01.30.Cc, 07.78.+s, 61.80.Jh, 61.82.Fk 1. Introduction The storage of nuclear waste products is a major con- cern of the nuclear industry. The ideal case would be to develop technologies which can eventually enable a partially- or fully-closed nuclear fuel cycle. This may include the reprocessing or alternative re-integration of nuclear waste products into the fuel cycle. Inert matrix fuel for the burn-up of plutonium and other minor actinides (MAs) is one of these proposed technologies currently under development. Inert matrix fuel involves the embedding of Pu and/or MAs in an in- ert matrix material in either a solid solution formation or a two-phase microstructure [1]. To determine the viabil- ity of candidate materials to use as inert matrices, their radiation tolerance to various sources of radiation need to be quantified. The types of radiation within the re- actor core include fission fragments (FFs), α -particles, γ -rays, etc. [1, 2]. The effects of FFs on the material microstructure is one of the qualifying criteria for inert matrices. Swift heavy ions (SHIs) are ideal for the simulation of FF radi- ation, because they have masses and energies comparable to those of FFs. The microstructural changes in the irra- diated material are studied within the current theoretical framework describing the interaction of SHIs with solids, called the thermal spike model [3]. Heavy ions with ener- gies > 100 keV/nucleon lose energy primarily by inelastic energy transfer mechanisms to the electronic subsystem * corresponding author; e-mail: arnojvv@gmail.com of the target material which may lead to the formation of latent ion tracks in some materials. Latent tracks may be amorphous, and may contain defects of a different phase than the unaffected material. The effects of ion ir- radiation on the microstructure of materials is of interest to both science and technology. In nuclear applications radiation effects limit the lifetime of reactor materials. The modelling and prediction of microstructural modifi- cation resulting from ion irradiation therefore holds con- siderable benefit [4]. The current investigation revolves around β -Si 3 N 4 , a ceramic which has an excellent combination of thermal (the thermal conductivity can range between 40–155 W/(m K), depending on the purity, grain size, and grain boundary film thickness [5]), electrical, and mechanical properties including a high melting temper- ature (≈ 1900 ◦ C), good oxidation and corrosion re- sistance, and also high strength at both room and elevated temperatures. Si 3 N 4 can exist in three crystal structures α -(trigonal), β -(hexagonal), and γ -phase (cubic). α-and β -phase are the most common forms of Si 3 N 4 [6, 7]. 2. Materials and methods Commercially available polycrystalline β-Si 3 N 4 ob- tained from MTI corporation was used in this inves- tigation. High energy ion irradiation of these samples was performed with the IC-100 cyclotron at the FLNR at the JINR in Dubna, Russia and with the DC-60 cy- clotron at the IRC in Astana, Kazakhstan. The tar- get materials were irradiated with Xe ions with ener- gies ranging from 167 to 220 MeV and fluences between (241)