Study of Changes in Optical and Heat-Conducting Properties of AlN Ceramics under Irradiation with Kr15+ and Xe22+ Heavy Ions

Abstract

AlN-based ceramics have great prospects for use in the field of structural materials for reactors of the new generation of GenIV, as well as dosimetric and optical devices. Interest in them is due to their unique physical and chemical properties, high resistance to degradation and excellent insulating properties. This work is devoted to the study of changes in the optical and heat-conducting properties of AlN ceramics as a result of irradiation with Kr15+ and Xe22+ heavy ions with energies close to those of fission fragments of uranium nuclei, and fluences 1014–1015 ion/cm2. During the study, dose relationships of changes in the optical properties of ceramics were established, as well as the effect of the type of ions on the degree of radiation damage and deterioration of optical characteristics. It has been found that an increase in the irradiation dose for Kr15+ ions leads to a slight increase in the depth of electron traps, while for samples irradiated with Xe22+ ions there is a sharp increase in the depth of occurrence from 5 to 20%, depending on the irradiation dose. For samples irradiated with Xe22+ ions, the greatest decrease in thermal conductivity was 19%, while for ceramics irradiated with Kr15+ ions, the maximum decrease was not more than 10%. The results show a significant resistance of ceramics to radiation damage by Kr15+ ions and negative effects, leading to a decrease in the resistance of optical and conductive properties of ceramics when irradiated with Xe22+ ions with doses higher than 5 × 1014 ion/cm2. Using the X-ray diffraction method, the dependences of structural distortions and changes in dislocation density in the structure of ceramics on the radiation dose were established. It has been determined that the main structural changes are associated with the fragmentation of grains, which result in an increase in the dislocation density, as well as deformation and distortion of the crystal lattice as a result of the formation of complex defects in the structure.

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

“…An increase in the irradiation fluence, and hence an increase in the probability of overlapping defect regions, leads to a decrease in the annihilation effect of point defects in the structure due to changes in the value of thermal vibrations of the crystal lattice, which leads to a decrease in thermal conductivity due to changes in the defect concentration in the damaged layer. Additionally, the small changes in the thermal conductivity of irradiated ceramics as compared to data from the literature [ 27 , 28 ] are due to the fact that the samples were irradiated at 1000 K, which contributes to the partial annealing of simple defects, such as vacancies, embedded atoms, or dislocations, which have a strong effect on the thermal conductivity of materials.…”

“…The most promising materials for new generation reactors are refractory ceramics based on oxides (MgAl 2 O 4 , BeO, Al 2 O 3 , ZrO 2 ), carbides (WC, TaC, SiC), and nitrides (AlN, BN, Si 3 N 4 ) [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Interest in them is caused by the possibility of their operation at increased temperatures, as well as in various aggressive environments, as they have high resistance to most types of acids and alkalis.…”