Neutron irradiation and post annealing effect on sapphire by positron annihilation.
Sapphire single crystals grown by an improved Kyropoulos-like method are irradiated by fast neutron flux. The irradiated doses of neutron are 10(18) and 10(19)n/cm(2). The infrared transmission spectra of sapphire were studied before and after irradiation. The irradiated samples were annealed at 200, 400, 600, 800 and 1000 degrees C for 10min in ambient atmosphere. Positron annihilation studies have been carried out before and after neutron irradiation. The experimentally measured positron lifetime in the pristine specimen is 143ps. There were aluminum vacancies produced in sapphire crystals after neutron irradiation. The positron lifetime increased with the dose of neutron flux. A longer value tau(2) was found after annealing at 600 degrees C, which indicated vacancies were aggregated with each other. The second long-time component tau(2) has been found to increase with the annealing temperature. There was almost no change in peak position of the CDB spectra after neutron irradiation and isothermal annealing. The chemical environment of core in sapphire did not change greatly after neutron irradiation.
Han
Jie-cai
JC
Center for Composite Materials, Harbin Institute of Technology, Nang Gang District, Harbin, China.
Zhang
Hai-liang
HL
Zhang
Ming-fu
MF
Wang
Bao-yi
BY
Li
Zhuo-xin
ZX
Xu
Cheng-hai
CH
Guo
Huai-xin
HX
D000537:Aluminum Oxide / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D006244:Hardness / Q000528:radiation effects; D009502:Neutrons; D011829:Radiation Dosage
D000537:Aluminum Oxide