Activation Energy of Electrical Conductivity and Characteristics of Microwave Radiation Absorption in AlN–SiC Composite

We investigated semiconductor composite materials of the AlN–50% SiC–Y₃Al₅O₁₂ system, obtained by free sintering, which exhibit a high level of microwave absorption of 4.6 dB/mm. The activation energy values of electrical conductivity (E_a) for the obtained composites were calculated within the temperature range of 20–800°C. At temperatures close to room temperature (20–150 °C), E_a ranges from 0.120 to 0.075 eV and increases to 0.270–0.275 eV as the temperature rises to 350–800°C. The determined photon energy values of the electromagnetic wave, in the frequency range from 1 to 100 GHz, are from 4.13 × 10^–6 to 4.13 × 10^–4 eV. Using quantum electrodynamics at the atomic level, we described the process of microwave radiation absorption in the AlN–SiC semiconductor composites. Low-energy photons of electromagnetic waves incident on the surface of the AlN–SiC composite transfer their energy to the conduction electrons in the near-surface layers of the SiC phase and are absorbed by them. The conduction electrons emit photons at the same frequency of the electromagnetic wave, predominantly into the same SiC grains, within 10^–8 s. This interaction results in the absorption of electromagnetic radiation, leading to the dissipation of wave energy and subsequent heating of the entire composite: initially, the SiC phase particles and, subsequently, the AlN grains.