Defects and Minor Phases in O+ and Zr+ Ion Co-implanted SrTiO3
This article reports on a comprehensive experimental study of 16O+ and 90Zr+ ion co-implanted SrTiO3 (STO) single crystals. In this study, STO is used as a model material to simulate a waste form for disposal of radioactive 90Sr that decays to 90Y and subsequently to 90Zr by emission of beta particles. Sequential implantation of 16O+ and 90Zr+ ions was performed at 550 K to balance the charge and to avoid full amorphization of STO. A number of experimental methods have been employed to characterize the implanted sample, including multiaxial ion channeling analysis and high-resolution x-ray diffraction. Results show that a high defect concentration was generated and accumulated in STO during the ion implantation, but the crystal structure was not rendered fully amorphous even for an atomic percentage of implanted O and Zr up to 1.5 at.% each. Thermal annealing at 1273 K leads to significant defect recovery at the surface with little recovery occurring at the damage peak, where a modest recovery is observed upon further annealing at 1423 K. Some of the implanted Zr species are well aligned with the STO <001> axis, but all are barely located at the substitutional sites. A minor phase with a tetragonal structure is observed in the Zr distributed region, which has the <001> axis parallel to that of the STO host. The tetragonal phase survives annealing at 1423 K with only a small decrease in the c value. A general assessment of this model waste form is also provided in this report.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1033828
- Report Number(s):
- PNNL-SA-77668; IECRED; 44713; 34930; AF5805000; TRN: US1200611
- Journal Information:
- Industrial and Engineering Chemistry Research, 51(2):621-628, Vol. 51, Issue 2; ISSN 0888-5885
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
ANNEALING
BETA PARTICLES
CRYSTAL STRUCTURE
DEFECTS
ION CHANNELING
ION IMPLANTATION
MONOCRYSTALS
WASTE FORMS
X-RAY DIFFRACTION
Ion implantation
Sr-90
SrTiO3
nuclear waste form
Environmental Molecular Sciences Laboratory