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 1 Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary 2 Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary 3 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 4 What is Li2+xTiO3+y ? CBBI @PortlandSep. 8 Li2O-TiO2Phase diagram 1155℃ β-Li2TiO3 +Li4TiO4 β-Li2TiO3 +Li5Ti4O12 β-Li2TiO3 (Monoclinic) phase maintains its phase 1.88 ≦ Li/Ti ≦ 2.25 [1] 51% Li2TiO3 Li2+xTiO3+y Li2+xTiO3+y Non-stoichiometric lithium titanate whose Li/Ti ratio is more than 2.0 5 [1] H. Kleykamp, Fusion Engineering and Design 61/62 (2002) 361/366 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. Li2+xTiO3+y had higher density than Li2TiO3 bigger crystal grain but, why ?? 6 Tritium residence in the pebbles CBBI @PortlandSep. 8 After T Production, T Behaviors in a blanket are H2 added sweep gas HTO etc. (4) T (2) (3) (1) (1)diffusion in grain (2)desorption at grain boundary (3)diffusion along grain boundary (4)desorption from particle surface and etc. Li2+xTiO3+y pebble In a blanket with H2 added sweep gas, process(1) is considered as on of a rate determining process[2] 7 [2] M. Nishikawa, A. Baba, Y. Kawamura, Journal of Nuclear Materials 246 (1997) 1-8 Tritium residence in the pebbles CBBI @PortlandSep. 8 After T Production, T Behaviors in a blanket are H2 added sweep gas HTO etc. (4) T (2) (3) (1) (1)diffusion in grain (2)desorption at grain boundary (3)diffusion along grain boundary (4)desorption from particle surface and etc. Li2+xTiO3+y pebble Average residence time under diffusion of T in the crystal grain [s] is θD = d2/60DT [2] d : Grain size [m] DT: The effective diffusivity of tritium in grain (m2/s) 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 8 Objective CBBI @PortlandSep. 8 Objective Objective To understand the detail of the sintering process of 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) 9 Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary 10 Synthesis CBBI @PortlandSep. 8 H2TiO3 LiOH・H2O Neutralization method Spin-mixing for 24h Gelled sample 2LiOH・H2O + H2TiO3→ Li2TiO3 + 4H2O Calcined at 500℃ Pellet Dummy pellet Sintered at 700~1200℃ in Ar Pellet SEM (coated with Osmium) Powder milled Alumina plate Powder XRD, TG 11 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=4.14276 c b -133 Intensity/ a.u. 50 Ti b 100 220 100 Intensity/ a.u. O 002 a 200 c Li a a=5.06707 b=8.77909 c=9.74970 β=100.2176 50 0 0 20 40 60 2θ/ °80 100 20 40 60 2θ/ °80 100 002 peak of β-Li2TiO3 is the diffraction from cation layer along c axis 12 Crystal structure Li2.1TiO3+y CBBI @PortlandSep. 8 Powder XRD patterns of the specimens Li2.1TiO3+y sintered at 500-800℃ 6000 5000 800℃ Intensity/ a.u. 4000 700℃ 2000 500℃ -133 002 3000 β-Li2TiO3(Monoclinic) 200 1000 α-Li2TiO3(Cubic) 0 10 20 30 40 50 60 70 80 90 100 All XRD pattern of 500℃ was attributed to α-Li2TiO3. Above 700℃, β-Li2TiO3(Monoclinic) started to formed 13 Crystal structure Li2.1TiO3+y CBBI @PortlandSep. 8 -133(β) 200(α) Li2.1TiO3+y Intensity/ a.u. 002(β) RT XRD patterns of Li2.1TiO3+y were measured after sinterig at 700~1200℃ 2θ/ ° 1200℃ 1150℃ 1100℃ 1050℃ 1000℃ 900℃ 800℃ 700℃ Intensity ratio of two peaks were calculated to roughly estimate the existing ratio of α and β phase 14 I002/I-133 of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 I002/I-133 was calculated from XRD patterns Ideal β-Li2TiO3 (simula on) Li2TiO3 Li2.1TiO3+y 2.5 I002/I-133 2 1.5 1 0.5 0 600 800 1000 1200 Sintering temperature ℃ - β-Li2TiO3 phase 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 β phases along c axis. 15 I002/I-133 of Li2TiO3 and Li2.1TiO3+y CBBI @PortlandSep. 8 I002/I-133 was calculated from XRD patterns Ideal β-Li2TiO3 (simula on) Li2TiO3 Li2.1TiO3+y 2.5 I002/I-133 2 1.5 1 0.5 0 600 800 1000 1200 Sintering temperature ℃ - β-Li2TiO3 phase 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 β phases along c axis. 16 Contents CBBI @PortlandSep. 8 1 Background 2 Objective 3 Synthesizing Li2+xTiO3+y 4 Crystal structure 5 Microstructure 6 Summary 17 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. 1100℃ 1150℃ 1200℃ Li2TiO3 10μm 10μm 10μm Li2.1TiO3+y 10μm 10μm 10μm 18 Grain of Li TiOLi Li2.13+y TiO3+y SEM ofsize Li2TiO and 3& 32 2.1TiO Grain size [μm] 20 CBBI @PortlandSep. 8 Li2TiO3 Li2.1TiO3+y 15 10 5 0 950 1000 1050 1100 1150 Tempareture [oC] 1200 1250 Gradual growth in Li2 TiO3 Significant growth in Li2.1TiO3 1100 →1150 → 1200℃ 19 Grain of Li TiOLi Li2.13+y TiO3+y SEM ofsize Li2TiO and 3& 32 2.1TiO Grain size [μm] 20 CBBI @PortlandSep. 8 Li2TiO3 Li2.1TiO3+y 15 10 5 0 950 1000 1050 1100 1150 Tempareture [oC] 1200 1250 Gradual growth in Li2 TiO3 Significant growth in Li2.1TiO3 1100 →1150 → 1200℃ Li2.1TiO3+y with small-homogeneous crystal grain at 1100℃ 20 Monoclinic ⇔Cubic transformation might be related to this phenomena Summary CBBI @PortlandSep. 8 The sintering process of Li2TiO3 and Li2.1TiO3+y were observed by 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 in Li2.1TiO3+y specimens. → considered to be Cubic + Monoclinic disordering. Li2.1TiO3+y specimens 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. 21 Thank you for your attention Portland 22 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 26