LOW-TEMPERATURE FAST-NEUTRON AND GAMMA-IRRADIATION OF ALUMINA

Structural stability of the plasma sprayed alumina has been studied af ter its exposure to 4 K fast-neutron and gamma irradiation. The fast-n eutron fluence (E > 0.1 MeV) was 1.8 x 10(22) n m(-2) AS shown by X-ra y diffraction and high-resolution transmission electron microscopy (HR TEM), the microstructure of alumina consisted of crystalline regions a nd regions which underwent considerable disordering (i.e. amorphizatio n) during plasma spray deposition. This microstructure has been basica lly preserved during irradiation. Consequently, the irradiation-induce d amorphization has not intervened at this neutron fluence. The light- brown appearance of the irradiated alumina indicated the formation of isolated point defects (colour centres). The accompanying near-isotrop ic swelling resulted in a small increase in lattice spacing, as measur ed by X-ray diffraction. The HRTEM provided no evidence for void forma tion in alumina during 4 K irradiation. (C) 1998 Elsevier Science Ltd. All rights reserved.