TY - JOUR
T1 - Positron and positronium studies of irradiation-induced defects and microvoids in vitreous metamict silica
AU - Hasegawa, M.
AU - Saneyasu, M.
AU - Tabata, M.
AU - Tang, Z.
AU - Nagai, Y.
AU - Chiba, T.
AU - Ito, Y.
N1 - Funding Information:
The neutron-irradiation was carried out under joint-use program at the Oarai Branch, Institute for Materials Research, Tohoku University. The ESR measurements were accomplished under the joint-use program JAERI facilities at the University of Tokyo. This work is partly supported by the Nippon Sheet Glass Foundation for Promoting Materials Engineering and a Grant-in-Aid for Scientific Research of the Ministry of Education, Science and Culture (No. 10450229).
PY - 2000/5/2
Y1 - 2000/5/2
N2 - To study irradiation-induced defects and structural microvoids in vitreous silica (v-SiO2), positron lifetime, angular correlation of positron annihilation radiation (ACAR), and electron spin resonance (ESR) were measured on v-SiO2 and quartz (c-SiO2) samples irradiated with fast neutrons up to a dose of 4.1×1020 n/cm2. Two kinds of positron-trapping defects have been found to form in v-SiO2 by fast neutron irradiation: type-I and type-II defects. Similar defects also appear in the irradiated c-SiO2, indicating that both the defects are common in v-SiO2 and c-SiO2. The detailed annealing and photo-illumination studies of positron annihilation and ESR for these two defects suggest that the type-I defects are non-bridging oxygen hole centers (NBOHC), while the type-II defects are oxygen molecules which cannot be detected by ESR. Higher dose irradiation than 1.0×1020 n/cm2 causes c-SiO2 to change to metamict (amorphous) phase (m-SiO2). Positronium (Ps) atoms are found to form in microvoids with an average radius of about 0.3 nm in the v-SiO2 and m-SiO2. This suggests that microvoids proved by Ps are structurally intrinsic open spaces and reflect the topologically disordered structure of these phases in the subnanometer scale.
AB - To study irradiation-induced defects and structural microvoids in vitreous silica (v-SiO2), positron lifetime, angular correlation of positron annihilation radiation (ACAR), and electron spin resonance (ESR) were measured on v-SiO2 and quartz (c-SiO2) samples irradiated with fast neutrons up to a dose of 4.1×1020 n/cm2. Two kinds of positron-trapping defects have been found to form in v-SiO2 by fast neutron irradiation: type-I and type-II defects. Similar defects also appear in the irradiated c-SiO2, indicating that both the defects are common in v-SiO2 and c-SiO2. The detailed annealing and photo-illumination studies of positron annihilation and ESR for these two defects suggest that the type-I defects are non-bridging oxygen hole centers (NBOHC), while the type-II defects are oxygen molecules which cannot be detected by ESR. Higher dose irradiation than 1.0×1020 n/cm2 causes c-SiO2 to change to metamict (amorphous) phase (m-SiO2). Positronium (Ps) atoms are found to form in microvoids with an average radius of about 0.3 nm in the v-SiO2 and m-SiO2. This suggests that microvoids proved by Ps are structurally intrinsic open spaces and reflect the topologically disordered structure of these phases in the subnanometer scale.
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U2 - 10.1016/S0168-583X(99)01026-5
DO - 10.1016/S0168-583X(99)01026-5
M3 - Conference article
AN - SCOPUS:0033746967
SN - 0168-583X
VL - 166
SP - 431
EP - 439
JO - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
JF - Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
T2 - 10th International Conference on Radiation Effects in Insulators
Y2 - 18 July 1999 through 23 July 1999
ER -