2019 Fiscal Year Research-status Report
Understanding equilibrium and non-equilibrium dopant segregation towards more stable electrode materials
| Project/Area Number |
18K13992
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| Research Institution | Kyushu University |
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Principal Investigator |
ハリントン ジョージ 九州大学, 持続的共進化地域創成拠点, 特任助教 (20753718)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | oxides / thin films / segregation / surfaces / grain boundaries |
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| Outline of Annual Research Achievements |
I have constructed an exchange rig allowing for oxygen tracer diffusion measurements and have performed tracer diffusion on epitaxial and polycrystalline films of LSM grown by PLD. LSM films have been fabricated on bi-crystal substrates of STO and YSZ to isolate the effects of individual grain bound
Rare-earth substituted ceria solid state solutions (Gd, Sm, Ho, Yb) has been synthesised, characterised using XRD, and polished to create well defined surfaces. These will allow the equilibrium driving forces for segregation to be assessed as a function of dopant size.
Oral presentations on the research have been given at the following conferences: ECS in Seattle, E-MRS in Strasburg, Electroceramics in Hassalt, Non-Stoichiometric Compounds in Miyazaki, SSI in PyeongChang, and ICE in Lausanne.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Although I have made excellent progress in fabricating well defined systems for study, there have been delays regarding the status of the low energy ion scattering (LEIS) equipment which is required to assess the extent of segregation to the surface. To ensure that progress is still being made, new avenues to characterise the films have been opened and a collaboration with the University of California, Irvine has been started where high-resolution vibrational electron-energy loss spectroscopy (VEELS) will be performed to carry out localised tracer diffusion in the TEM. Combined with the LEIS measurements, which will be carried out in the near future, will provide a detailed view of the behaviour of diffusion at grain boundaries and the driving forces for segregation in the bulk.
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| Strategy for Future Research Activity |
Assessing the surface segregation to the surface of ceria solid state solutions (Gd, Sm, Ho, Yb) will be carried out in the coming months using LEIS, as well as initial VEELS and ToF-SIMS measurements on individual grain boundaries in LSM films. The collaboration with the University of California, Irvine will be supported by an grant proposal which will be soon submitted to the USA National Science Foundation (NSF). Papers on the findings will be written up and submitted to international, peer-reviewed, journals.
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| Causes of Carryover |
Due to issues with the availability of the LEIS system caused by necessary maintenance, part of the research expenditure will be used in the next fiscal year to perform LEIS measurements on the samples which have been previously fabricated.
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