Irradiation-Induced Aggregate Centers in Single Crystal Al2O8

Abstract

Aggregate centers in reactor irradiated single crystal a-,41,0, are investigated using the thermochemical and photochemical methods. Isochronal and isothermal annealing5 of the bands at 302, 356, 450, and 570 nm are performed in detail to study the thermal stability and to obtain the activation energy ( E ) for the decay of their corresponding centers. After X-ray irradiation at room temperature, a new band at 384 n m appears in the crystal irradiated previously by reactor radiation. From the thermochemical and photochemical properties as well ns from correlations of these several bands, i t is proposed tentatively that the 450 and 570 nm bands are attributed to the Fi type center, and the 302 nm band to the F, center.Mittels thermochemischer und photochemischer Methoden werden Aggregatzentren in Reaktorbestrahlten cc-Al,O,-Einkristallen untersucht. Isochrone und isotherme Temperungen der Banden bei 302, 356,450 und 570 nm werden durchgefiihrt, um die thermische Stabilitat zu untersuchen und die Aktivierungsenergie ( E ) fur den Zerfall ihrer entsprechenden Zentren zu erhnlten. Xach Rontgenbestrahlung bei Zimmertemperatur tritt eine neue Bande bei 384 nm in den vorher im Reaktor bestrahlten Kristallen auf. Aus den thermochemischen und photochemischen Eigenschaften sowie aus den Korrelationen dieser verschiedenen Canden wird vorlaufig angenommen, daB die 450 und 570 nm-Randen dem FS-Zentrum und die 302 nm-Bande dem F,-Zentrum zugeordnet sind.

Thermal conductivity degradation of ceramic materials due to low temperature, low dose neutron irradiation

“…The 0.01 dpa data suggest that a dominant defect annealing stage occurs near 600°C. Previous optical spectroscopy studies on sapphire irradiated under similar conditions as the present study [42,[54][55][56] have observed several distinct annealing stages in the temperature range from 100 to 800°C, which are associated with the formation or dissociation of different types of small defects. For example, annealing of oxygen monovacancies occurs in a broad temperature range extending from $100°C (i.e., immediately above the irradiation temperature) up to $700°C, and oxygen divacancy annealing stages (F 2 , F þ 2 , etc.)…”

AFM and photoluminescence studies of swift heavy ion induced nanostructured aluminum oxide thin films

“…Therefore, it is believed that 540 nm emission observed in the present work may be due to such F 2 2+ -centers. Atobe et al [21] studied irradiation induced aggregate centers in single crystal of Al 2 O 3 . They reported an optical absorption band with a peak at 450 nm after irradiation with 10 17 neutrons cm À2 , which they attributed to F 2 + -centers.…”

Production and reaction kinetics of radiation-induced defects in α-alumina and sapphire under ion beam irradiation

“…3, one would expect the observation of the F x in the present specimens. In fact, such aggregate centers as F þ 2 and F 2 have been identified to be formed in neutron-irradiated single crystal a-Al 2 O 3 [10]. For comparison, some specimens of sapphire in the present study were subjected to the absorption measurement, but only a slight and broad absorption was observed over the range studied from 200 to 800 nm.…”