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

[email protected]

1

Contents CBBI @PortlandSep. 8

1 Background2 Objective3 Synthesizing Li2+xTiO3+y

4 Crystal structure5 Microstructure6 Summary

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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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