Radiation defect-formation in steatite ceramics

Full text: Ceramic materials are broadly used in different area of science and technology lately. They have also proved themselves to be radiation-resistant material in modern nuclear-physical instruments. Studying radiation characteristics of the industrial ceramics SK-1 [1], we have discovered structured defects at high-dose-irradiation (>109R). They were considered as surface defects formed on the border between crystalline (metallic silicate of magnum-MgSiO3) and glassy phase by break up of Si-O-Mg bond because of the polarizing actions of Mg cations and formation Si3+O-Mg bond. The defect E1-centre has the absorption band (AB) at 220 nm. In the present work, spectra of diffuse reflections (DR) of γ and n- γ-irradiated sample of the SK-1 ceramics were studied. The DR spectrum has AB with maximum at 260 nm and a few broad AB in the visible range with maxima at 400, 480 and 550 nm. The band at 260 nm was identified as Fe3+, and those at 400, 480 and 550 nm are three varieties of V- centres. Similar picture was observed in the samples after n-γ-irradiation in the reactor. The study of difference spectra of DR prior and after n- γ-irradiation (∇ R=Rγ - Rn-γ ) has shown that except above specified AB, one more was found with maximum at 620-630 nm, which is typical to for absorption of non-bridging oxygen hole center (NBOHC) formed under the irradiation. The distinctive feature of NBOHC is its AB at 260 and 620 nm and luminescence at 660 nm. The intensity of AB at 660 nm is very weak and appears at high γ-dose (≥109 P). Efficiency of the creation of V-centre in irradiated samples is much higher than NBOHC. In n-γ-irradiated sample AB caused by NBOHC are seen clearly. We expect that AB with maximum at 400 nm is caused by cation vacancy in MgO, other two centres are -O-Me like states. Possible mechanisms are suggested for explaining formation of V-centres and NBOHC in steatite ceramics SK-1 during γ and n- γ-irradiation in the reactor. References: 1. Gasanov E.M, Kim Gen Chan, Saidahmedov K.H. The spectra of the optical absorption of irradiated steatite ceramics, Atomic Energy, 1998, vol. 85. n3, p.258-259. (authors)