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Growth Control of Li 2+x TiO 3+y for an Advanced Tritium Breeding Material

Growth Control of Li 2+x TiO 3+y for an Advanced Tritium Breeding Material. Keisuke Mukai (Ph.D. student) , Kazuya. Sasaki, Takayuki Terai , Akihiro Suzuki, Tsuyoshi. Hoshino. The University of Tokyo School of Engineering, Department of Nuclear Engineering and Management.

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Growth Control of Li 2+x TiO 3+y for an Advanced Tritium Breeding Material

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  1. Growth Control of Li2+xTiO3+y for an Advanced Tritium Breeding Material Keisuke Mukai (Ph.D. student), Kazuya. Sasaki, Takayuki Terai, Akihiro Suzuki, Tsuyoshi. Hoshino The University of Tokyo School of Engineering, Department of Nuclear Engineering and Management kmukai@nuclear.jp

  2. Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary

  3. Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary

  4. Background CBBI @PortlandSep. 8 Li2TiO3 (Lithium Meta-titanate) ○High chemical stability&Good Tritium release property ☓Lower Li density than other candidates (ex. Li2O, Li4SiO4) Li2+xTiO3+y ( Lithium meta-titanate with excess Li ) is expected as an advanced breeding material due to its higher Li density

  5. What is Li2+xTiO3+y ? CBBI @PortlandSep. 8 Li2O-TiO2Phase diagram 1155℃ β-Li2TiO3(Monoclinic) phase maintains its phase 1.88≦ Li/Ti ≦ 2.25 [1] β-Li2TiO3 +Li4TiO4 β-Li2TiO3 +Li5Ti4O12 51% Li2TiO3 Li2+xTiO3+y Non-stoichiometric lithium titanate whose Li/Tiratio is more than 2.0 Li2+xTiO3+y [1] H. Kleykamp, Fusion Engineering and Design 61/62 (2002) 361/366

  6. Previous study CBBI @PortlandSep. 8 Li2TiO3 Li-rich 10μm 10μm 10μm SEM images on the cross sections of the sintered pellets at 1200℃ for 1h. higher density bigger crystal grain Li2+xTiO3+yhad than Li2TiO3 but, why ??

  7. Tritium residence in the pebbles CBBI @PortlandSep. 8 After T Production, T Behaviors in a blanket are H2 added sweep gas (1)diffusion in grain (2)desorption at grain boundary (3)diffusion along grain boundary (4)desorptionfromparticlesurface and etc. HTO etc. T (2) (4) (3) (1) Li2+xTiO3+y pebble In a blanket with H2 added sweep gas, process(1) is considered as on of a rate determining process[2] [2] M. Nishikawa, A. Baba, Y. Kawamura, Journal of Nuclear Materials 246 (1997) 1-8

  8. Tritium residence in the pebbles CBBI @PortlandSep. 8 After T Production, T Behaviors in a blanket are H2 added sweep gas (1)diffusion in grain (2)desorption at grain boundary (3)diffusion along grain boundary (4)desorptionfromparticlesurface and etc. HTO etc. T (2) (4) (3) (1) Li2+xTiO3+y pebble Average residence time under diffusion of T in the crystal grain [s] is d : Grain size[m] DT: The effective diffusivity of tritium in grain (m2/s) θD = d2/60DT [2] Li2+xTiO3+y pebbles with smaller grains are needed to decrease tritium inventory in the pebbles. [2] M. Nishikawa, A. Baba, Y. Kawamura, Journal of Nuclear Materials 246 (1997) 1-8

  9. Objective CBBI @PortlandSep. 8 Objective Objective To understand the detail of the sintering processof Li2+xTiO3+y for the fabrication of the pebbles with smaller grain Sample: Li2TiO3 & Li2.1TiO3+y ●Crystallization Powder X-ray Diffraction (PXRD) Rietan FP (simulation) ●Microstructure Scanning electron microscope (SEM)

  10. Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary

  11. Synthesis CBBI @PortlandSep. 8 H2TiO3 LiOH・H2O Neutralization method Spin-mixing for 24h Gelled sample 2LiOH・H2O + H2TiO3→ Li2TiO3 + 4H2O Calcinedat 500℃ Dummy pellet Pellet Sintered at 700~1200℃ in Ar Pellet SEM (coated with Osmium) Powder milled Powder Alumina plate XRD, TG

  12. XRD peak simulation CBBI @PortlandSep. 8 • XRD peaks of α-Li2TiO3 and β-Li2TiO3 were calculated by Rietan-FP α-Li2TiO3 cubic (low temp. structure) β-Li2TiO3 (monoclinic) (Below 1155℃[]) a=5.06707 b=8.77909 c=9.74970 β=100.2176 a=4.14276 c b a c a b 200 002 -133 Intensity/ a.u. 220 Intensity/ a.u. 2θ/ ° 2θ/ ° 002 peak of β-Li2TiO3 is the diffraction from cation layer along c axis

  13. Crystal structure Li2.1TiO3+y CBBI @PortlandSep. 8 Powder XRD patterns of the specimens Li2.1TiO3+ysintered at 500-800℃ 800℃ Intensity/ a.u. 700℃ 500℃ 002 -133 β-Li2TiO3(Monoclinic) 200 α-Li2TiO3(Cubic) All XRD pattern of 500℃ was attributed to α-Li2TiO3. Above 700℃, β-Li2TiO3(Monoclinic)started to formed

  14. Crystal structure Li2.1TiO3+y CBBI @PortlandSep. 8 RT XRDpatterns of Li2.1TiO3+ywere measured after sinterigat 700~1200℃ 200(α) 002(β) -133(β) Intensity ratio of two peaks were calculated to roughly estimate the existing ratio of α and βphase

  15. I002/I-133of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 I002/I-133 was calculated from XRD patterns Sintering temperature ℃ - β-Li2TiO3phase mostly formed above 1000℃(Li2TiO3) and above 900℃ (Li2.1TiO3+y) - I002 peak of Li2.1TiO3+y sintered above 1100℃ became broadened. → This is considered to be due to the stacking fault of α and βphases along c axis.

  16. I002/I-133of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 I002/I-133 was calculated from XRD patterns Sintering temperature ℃ - β-Li2TiO3phase fully formed above 1000℃(Li2TiO3) and above 900℃ (Li2.1TiO3+y) - I002 peak of Li2.1TiO3+y sintered above 1100℃ became broadened. → This is considered to be due to the stacking fault of α and βphases along c axis.

  17. Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary

  18. SEM of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 SEM images (☓2500) on the cross sections of the sintered pellets at 1100~1200℃ for 1h.

  19. Grain size of Li2TiO3 & Li2.1TiO3+y SEM of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 CBBI @PortlandSep. 8 Li2TiO3 Li2.1TiO3+y • Gradual growth in Li2 TiO3 • Significant growth in Li2.1TiO3 1100 →1150 → 1200℃ 

  20. Grain size of Li2TiO3 & Li2.1TiO3+y SEM of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 CBBI @PortlandSep. 8 Li2TiO3 Li2.1TiO3+y • Gradual growth in Li2 TiO3 • Significant growth in Li2.1TiO3 1100 →1150 → 1200℃  Li2.1TiO3+y with small-homogeneous crystal grain at 1100℃ Monoclinic ⇔Cubic transformation might be related to this phenomena

  21. Summary CBBI @PortlandSep. 8 The sintering process of Li2TiO3and Li2.1TiO3+y were observedby investigating crystal growth and crystal strucuture. • Ordered monoclinic β-phase was obtained above 1000℃ (Li2TiO3) and 900℃ (Li2.1TiO3+y). Above 1100℃, peak broadening were found inLi2.1TiO3+yspecimens. → considered to be Cubic + Monoclinic disordering. • Li2.1TiO3+yspecimens sintered above 1100℃ had the larger grain growth than Li2TiO3. From the view point of tritium inventory in ceramic breeder, sintering temperature is needed to be less than 1100℃ . High temperature XRD and Rietveld analysis are planed to understand the existing ratio of cubic & monocloinic and transformation temperature.

  22. Thank you for your attention Portland

  23. Quotation A. Lauman, K. Thomas Felh, et al. Z. Kristallogr 226(2011)53-61

  24. Quotation Li2MnO3 A. Boulineau, L. Croguennec, et al. Solid State Ionics 180(2010)1652-1659

  25. Introduction CBBI @PortlandSep. 8 Terai-Suzuki Lab. ・Liquid Li purification ・H2 permeation barrier ・Ceramic breeder ・HLW reprocessing . . etc. Chemical and Thermal property of ceramic breeder (lithium titanate) are mainly investigated under BA

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