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

Growth Control of Li2+xTiO3+y for an Advanced Tritium Breeding Material

The University of TokyoSchool of Engineering,

Department of Nuclear Engineering and Management

Keisuke Mukai (Ph.D. student), Kazuya. Sasaki, Takayuki Terai, Akihiro Suzuki, Tsuyoshi. Hoshino

kmukai@nuclear.jp

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Contents CBBI @PortlandSep. 8

1 Background2 Objective3 Synthesizing Li2+xTiO3+y

4 Crystal structure5 Microstructure6 Summary

2

Contents CBBI @PortlandSep. 8

1 Background2 Objective3 Synthesizing Li2+xTiO3+y

4 Crystal structure5 Microstructure6 Summary

3

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

Background CBBI @PortlandSep. 8

4

β-Li2TiO3 (Monoclinic) phase maintains its phase

1.88 Li/Ti 2.25 ≦ ≦ [1]

Non-stoichiometric lithium titanatewhose Li/Ti ratio is more than 2.0

Li2+xTiO3+y

β-Li2TiO3

+Li4TiO4 β-Li2TiO3

+Li5Ti4O12

51%

Li2O-TiO2Phase diagram

[1] H. Kleykamp, Fusion Engineering and Design 61/62 (2002) 361/366

Li2TiO3

Li2+xTiO3+y

CBBI @PortlandSep. 8What is Li2+xTiO3+y ?

1155℃

5

Li2TiO3

10μm 10μm 10μm

Li-rich

higher densitybigger crystal grain

Li2+xTiO3+y had

SEM images on the cross sections of the sintered pellets at 1200 ℃ for 1h.

but, why ?? 6

CBBI @PortlandSep. 8Previous study

than Li2TiO3

H2 added sweep gas （ 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

After T Production, T Behaviors in a blanket are

HTO etc. T

In a blanket with H2 added sweep gas, process(1) is considered as on of a rate determining process[2]

(4)(1)

(2)(3)

CBBI @PortlandSep. 8Tritium residence in the pebbles

[2] M. Nishikawa, A. Baba, Y. Kawamura, Journal of Nuclear Materials 246 (1997) 1-87

H2 added sweep gas

Li2+xTiO3+y pebble

After T Production, T Behaviors in a blanket are

Li2+xTiO3+y pebbles with smaller grains are needed to decrease tritium inventory in the pebbles.

(4)(1)

(2)(3)

d : Grain size 　 [m]DT: The effective diffusivity of tritium in grain (m2/s)θD = d2/60DT

（ 1 ） diffusion in grain（ 2 ） desorption at grain boundary（ 3 ） diffusion along grain boundary（ 4 ） desorption from particle surface and etc.

HTO etc. T

[2]

[2] M. Nishikawa, A. Baba, Y. Kawamura, Journal of Nuclear Materials 246 (1997) 1-8

CBBI @PortlandSep. 8Tritium residence in the pebbles

Average residence time under diffusion of T in the crystal grain [s] is

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ObjectiveObjective

CBBI @PortlandSep. 8Objective

●Crystallization　　 Powder X-ray Diffraction (PXRD) Rietan FP (simulation) ●Microstructure Scanning electron microscope (SEM)

Sample: Li2TiO3 & Li2.1TiO3+y

To understand the detail of the sintering process of Li2+xTiO3+y for the fabrication of the pebbles with smaller grain

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Contents CBBI @PortlandSep. 8

1 Background2 Objective3 Synthesizing Li2+xTiO3+y

4 Crystal structure5 Microstructure6 Summary

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Neutralization method

Calcined at 500℃

Gelled sample

LiOH ・H2O

H2TiO3

Spin-mixing for 24h

Sintered at 700 ～ 1200 in Ar℃

2LiOH ・ H2O + H2TiO3→ Li2TiO3 + 4H2O

SEM (coated with Osmium)

XRD, TGPowder

Pellet

milled

Pellet

Powder

Dummy pellet

Alumina plate

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CBBI @PortlandSep. 8Synthesis

20 40 60 80 100

0

50

100

20 40 60 80 100

0

50

100

002

-133

200

220

Inte

nsity

/ a.u

.

2θ/ °

Inte

nsity

/ a.u

.

2θ/ °

Li

O

Ti

α-Li2TiO3 cubic(low temp. structure)

β-Li2TiO3 (monoclinic)(Below 1155 [])℃

a=4.14276 a=5.06707 b=8.77909 c=9.74970 β=100.2176

XRD peaks of α-Li2TiO3 and β-Li2TiO3 were calculated by Rietan-FP

002 peak of β-Li2TiO3 is the diffraction from cation layer along c axis

ab

c

a

b

c

CBBI @PortlandSep. 8XRD peak simulation

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α-Li2TiO3(Cubic)

β-Li2TiO3(Monoclinic)

500℃

700℃

800℃

Inte

nsity

/ a.u

.Powder XRD patterns of the specimens Li2.1TiO3+y sintered at 500-800℃

200

002

-133

All XRD pattern of 500 was attributed to α-Li℃ 2TiO3.

Above 700 , β-Li℃ 2TiO3(Monoclinic) started to formed

CBBI @PortlandSep. 8Crystal structure Li2.1TiO3+y

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RT XRD patterns of Li2.1TiO3+y were measured after sinterig at 700 ～ 1200℃

Intensity ratio of two peaks were calculated to roughly estimate the existing ratio of α and β phase

002(

β)

-133

(β)

200(

α)

CBBI @PortlandSep. 8Crystal structure Li2.1TiO3+y

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I002/I-133 was calculated from XRD patterns

Sintering temperature ℃ - β-Li2TiO3 phase mostly formed above 1000 (Li℃ 2TiO3) and above 900 (Li℃ 2.1TiO3+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.

CBBI @PortlandSep. 8I002/I-133 of Li2TiO3 and Li2.1TiO3+y

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- β-Li2TiO3 phase fully formed above 1000 (Li℃ 2TiO3) and above 900 (Li℃ 2.1TiO3+y)

I002/I-133 was calculated from XRD patterns

Sintering temperature ℃

- 　 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.

CBBI @PortlandSep. 8I002/I-133 of Li2TiO3 and Li2.1TiO3+y

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Contents CBBI @PortlandSep. 8

1 Background2 Objective3 Synthesizing Li2+xTiO3+y

4 Crystal structure5 Microstructure6 Summary

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SEM images ( 2500) on the cross sections of the sintered pellets at 1100☓ ～ 1200 for 1h.℃

CBBI @PortlandSep. 8SEM of Li2TiO3 and Li2.1TiO3+y

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Significant growth in Li2.1TiO3 1100 →1150 → 1200℃ 　 Gradual growth in Li2 TiO3

Li2TiO3 Li2.1TiO3+y

CBBI @PortlandSep. 8Grain size of Li2TiO3 & Li2.1TiO3+y CBBI @PortlandSep. 8SEM of Li2TiO3 and Li2.1TiO3+y

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Significant growth in Li2.1TiO3 1100 →1150 → 1200℃ 　 Gradual growth in Li2 TiO3

CBBI @PortlandSep. 8Grain size of Li2TiO3 & Li2.1TiO3+y

Li2.1TiO3+y with small-homogeneous crystal grain at 1100℃Monoclinic Cubic transformation might be related to this phenomena⇔

CBBI @PortlandSep. 8SEM of Li2TiO3 and Li2.1TiO3+y

Li2TiO3 Li2.1TiO3+y

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CBBI @PortlandSep. 8Summary

The sintering process of Li2TiO3 and Li2.1TiO3+ywere observed by investigating crystal growth and crystal strucuture.

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.

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.

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Thank you for your attention

Portland22

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Quotation

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

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Li2MnO3

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

Quotation

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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