Radiation-induced defects in LiAlO2 crystals: Holes trapped by lithium vacancies and their role in thermoluminescence

Holston, Maurio S.; McClory, John W.; Giles, N. C.; Halliburton, L. E.

doi:10.1016/j.jlumin.2014.11.018

Cited by 42 publications

(13 citation statements)

References 29 publications

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“…Tritium must be produced to secure a steady supply as it is subject to decay with a half-life of 12.3 years. When LiAlO 2 is irradiated under a neutron flux, 3 H and 4 He particles from reaction 6 Li(n,) 3 H will be emitted at energies of 2.75 and 2.05 MeV, respectively. These energetic particles will initiate damage cascades that lead to generation of point defects in the crystal structure.…”

Section: Introductionmentioning

confidence: 99%

“…The accumulation of point defects, formation of extended defects and presence of gas species in LiAlO 2 are expected to affect the structural stability, thermomechanical properties, and tritium migration. Previous studies of LiAlO 2 reported in the literature have addressed technical issues of structural defects, volume swelling, micro-cracking, tritium detrapping, diffusion and release using various radiation sources, including x-rays and -rays [4,5], electrons [6,7], neutrons [8][9][10][11][12], and ions [13][14][15]. Modeling of tritium transport [16][17][18] and molecular dynamics (MD) calculations of threshold displacement energies [19], defect production [20,21] and Li diffusion [22] have also been carried out.…”

Section: Introductionmentioning

confidence: 99%

“…However, very few quantitative studies of damage accumulation in LiAlO 2 have been reported to date. Katsui et al used 2 H (surrogate for 3 H) and 4 He ions to irradiate -LiAlO 2 single crystals at room temperature [23,24] and found a sigmoidal-type dependence of defect concentrations on dose, similar to the generic behavior of many other ceramic materials, such as SiC [25], GaN [26], and SrTiO 3 [27]. The dose-dependent defect accumulation in -LiAlO 2 at elevated temperatures, such as ~573 K that is applied at the Watts Bar Nuclear Unit 1 commercial power plant [28] for tritium production, is currently unknown; tritium diffusion kinetics are subject to change as microstructure evolves.…”

Section: Introductionmentioning

confidence: 99%

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Irradiation effects and hydrogen behavior in H2+ and He+ implanted γ-LiAlO2 single crystals

Jiang

Zhang

Kovařík

et al. 2017

Journal of Nuclear Materials

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Gamma-phase lithium aluminate (-LiAlO 2 ) is a breeder material for tritium, a necessary substance for strategic stockpile and fusion power systems. A fundamental study of structural evolution and tritium diffusion in -LiAlO 2 under displacive irradiation is needed to fully assess the material performance. This study utilizes ion implantation of protium (surrogate for tritium) and helium in -LiAlO 2 single crystals at elevated temperatures to emulate the irradiation effects. The results show that at 573 K there are two distinct disorder saturation stages to 1 dpa without full amorphization; overlapping implantation of H 2 + and He + ions suggests possible formation of gas bubbles. For irradiation to 10 21 H + /m 2 (0.36 dpa at peak) at 773 K, amorphization occurs at surface with H diffusion and dramatic Li loss; the microstructure contains bubbles and cubic LiAl 5 O 8 precipitates with sizes up to 200 nm or larger. In addition, significant H diffusion and release are observed during thermal annealing.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Irradiation effects and hydrogen behavior in H2+ and He+ implanted γ-LiAlO2 single crystals

Jiang

Zhang

Kovařík

et al. 2017

Journal of Nuclear Materials

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“…Even before the diffusion treatment, there appear to be very few (if any) isolated lithium vacancies in the as-grown LiGaO 2 crystals. In undoped LiAlO 2 crystals, an intense 11-line EPR signal is seen after an x-ray irradiation at room temperature when holes are trapped on O 2 ions adjacent to lithium vacancies [17]. An analogous trapped-hole EPR signal is not seen in undoped LiGaO 2 crystals after irradiating with x rays at room temperature or at 77 K.…”

Section: Electron Paramagnetic Resonance (Epr)mentioning

confidence: 95%

Green luminescence from Cu-diffused LiGaO2 crystals

Holston

Ferguson

Giles

et al. 2016

Journal of Luminescence

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An intense green luminescence is observed from single crystals of LiGaO 2 doped with copper. Czochralski-grown undoped crystals are wrapped in thin copper foil and then held at 900 °C for 1 h in a flowing nitrogen atmosphere. Large concentrations of Cu + ions enter the crystals during this process and occupy Li + sites. These copper-diffused crystals are characterized with optical absorption, photoluminescence (PL), photoluminescence excitation (PLE), thermoluminescence (TL), and electron paramagnetic resonance (EPR). An optical absorption band peaking near 350 nm is assigned to the Cu + ions at Li + sites and represents an excitation from a 3d 10 ground state to a 3d 9 4s 1 excited state. A broad PL emission from these excited Cu + ions has a peak near 523 nm and the related PLE band has a peak near 356 nm (this PLE band links the emission to the optical absorption band). Illuminating a Cu-diffused crystal at room temperature with 325 nm laser light converts a portion of the Cu + ions to Cu 2+ ions. EPR spectra from these 3d 9 ions are easily seen at low temperatures and their angular dependence is used to determine the g matrix and the 63 Cu hyperfine matrix. Subsequent heating produces a TL peak near 122 °C with a maximum in its spectral dependence near 535 nm. Correlated EPR measurements show that this TL peak occurs when trapped electrons are thermally released from unintentionally present transition-metal ions (most likely Fe) and recombine with holes at the Cu 2+ ions.

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“…8 include a holelike g value of 2.019 and a hyperfine parameters previously found for a trapped hole on an oxygen ion next to a lithium vacancy in LiAlO 2 crystals. 45 The defects responsible for the remaining EPR lines in Fig. 8 Heating to this temperature causes all of the interstitials to recombine with oxygen vacancies (see …”

Section: E Epr Spectrum From the Aluminum Vacancymentioning

confidence: 99%