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Kazarinov

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Kazarinov 18.10.2017

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Kazarinov

  1. 1. 1 / 4 SPECTROSCOPIC STUDIES OF DEFECTS IN GAMMA- AND NEUTRON-IRRADIATED MAGNESIUM ALUMINATES SPINEL CERAMICS Yu. Kazarinov, V. Kvatchadze, V. Gritsyna, M. Abramishvili, Z. Akhvlediani,M. Galustashvili, G. Dekanozishvili, T. Kalabegishvili, V. Tavkhelidze
  2. 2. Introduction and Objectives •MAS structure contain high concentration of vacant positions • Anti-site defects concentration up to 2-3 % at. •Ability to incorporate wide range of impurities Fragment of structure MgAl2O4 2 / 4
  3. 3. Introduction and Objectives •Magnesium aluminate spinel (MgAl2O4) – highly radiation resistant material •Insulator for magnetic system for ion beam separators •High speed (τ=4.55ns) Scintillator for α-particles •Long time (10 hours) bright Luminofor 3 / 4
  4. 4. Introduction and Objectives •Exellent transmission in the UV-VIS-Mid IR wavelength range •Good mechanical properties •Technology of production of spinel of high volumes was developed 4 / 4
  5. 5. Experimental details Ceramics samples preparation MgAl2O4:LiF (1 wt.%) Hot Pressing in vacuum •1550ºC •35 MPa Irradiation • 60 Co. 2.4 Gy/min • WWR: up to 5·1013 n/cm2 • Electrons: 16MeV. Dose 1.1·1017 el/cm2 Annealing 30 min. step 50ºC 30 sec. step 50ºC Investigation methods •Optical spectra: •UV-NIR - SF-29 •IR - Specord 75 •EPR - RE 1306 •Radiluminescence •Cu. U=40 kV, I=0.4 mA •MDR-1 •FEU-106 (200-800 nm) 5 / 4
  6. 6. Radiation induced UV-Vis optical centers in spinel ceramics Gamma-radiation-induced absorption spectra spinel ceramics irradiated to different doses 6 / 4 Absorption spectra of spinel ceramics before irradiation, and gamma-neutron irradiation- induced absorption spectra
  7. 7. Radiation induced IR optical centers in spinel ceramics 7 / 4 IR transmission spectra of MAS ceramics: Inset: EPR spectrum of γ-irradiated MAS ceramics Dose dependences of 1556 cm-1 , intensity band at 3.7 eV and EPR signal on the γ-irradiation dose
  8. 8. Radioluminescence in insulators ( )1 exc traps gap E h V C E ν µ × Excited volume hνhνhνhνhνhνhν Luminescence centers hν Cr UV Mn 8 / 4 Spectrum of the steady-state radio- luminescence (SSRL) of spinel ceramics
  9. 9. 9 / 4 ● Radiation defects relaxation 2nd stage: cation defects recombination 3nd stage: anion defects recombination Annealing of F-centers in γ-n irradiated ceramics SSRL intensity dependence on annealing temperature in e-irradiated ceramics
  10. 10. Conclusion •MgAl2O4 spinel ceramics during low dose γ and γ -neutron irradiation formed optical centers at existing defects •Spinel ceramics have carbon and peroxy impurities due to technology peculiarities •Two stage annealing of cation and anion radiation defects complexes was revealed at 250ºC 10 / 4
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