Irradiated cubic single crystal SiC as a high temperature sensor
Radiation is known to cause point defects formation in different materials. In the case of cubic SiC single crystal radiation flux on the order of 2⋅10 20 neutrons/cm 2 at 0.18 MeV causes over 3% volume lattice expansion. Radiation-induced strain (measurable by X-Ray diffraction) can be relieved when the annealing temperature exceeds the temperature of irradiation. Based on this effect the original technology of maximum temperature measurement was developed a while ago. Single crystal SiC sensor small size (200-500 microns), wide temperature range (150-1450 °C), “no-lead” installation, and exceptional accuracy make it very attractive for use in small, rotating and “hard-to-access” parts, including, but not limited to gas turbine blades, space shuttle ceramic tiles, automobile engines, etc. With the advances in X-Ray diffraction measurements, crystal and thin film growth techniques, it is the time to revise and update this technology. Modeling radiation damage, as well as annealing effects are also beneficial.
Irradiated Single Crystal 3C-SiC as a Maximum Temperature Sensor
xi Chapter
Structural changes induced by helium ion irradiation in silicon carbide crystals
Electron microscopic observations were performed on defect structures in polycrystalline SiC crystals irradiated with 30 keV He ions to fluences from 1014 to 1017 ions/cm2. A number of defect clusters were observed which were hexagonal in shape when observed from the c-axis direction but were seen to be of linear form when viewed from a direction parallel to the c-plane. These clusters increased in density with increasing irradiation fluence, and were considered to be formed by the agglomeration of irradiation-produced point defects or the injected helium atoms on the c-planes. 
 
Amorphization was observed for a fluence above a critical value of 7 × 1015 ions/cm2 which corresponds to about one dpa for the 30 keV helium ions incident at random orientations on a SiC crystal. Irradiations of this critical fluence were unable to cause amorphization in the ion channeling directions. Heavy irradiations at the high temperature of 1000 K resulted in a number of fine crystallites, that is, recrystallized zones.