Electrical Properties of Annealed and Coated Boron Nitride Under Electron Beam Irradiation
The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminum oxide (BN/Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an–BN/Al2O3) were investigated under low power electron irradiation (5 < incident energy E0 < 20 keV and incident flux Ji = 10 nA cm-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an BN/Al2O3 sample was carried out under a critical electron flux (E0 = 20 keV and Ji = 750 nA cm-2) in order to assess the degradation kinetics of the material’s electrical properties. The characterizations of an–BN/Al2O3 samples were performed before and after electrical aging at CIRIMAT (Toulouse, France) to identify the structural and chemical evolution which would explain this degradation. A chemical deterioration of coating and some contaminants were observed after the critical irradiation.