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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

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

slide2

Contents

CBBI @PortlandSep. 8

1 Background

2 Objective

3 Synthesizing Li2+xTiO3+y

4 Crystal structure

5 Microstructure

6 Summary

slide3

Contents

CBBI @PortlandSep. 8

1 Background

2 Objective

3 Synthesizing Li2+xTiO3+y

4 Crystal structure

5 Microstructure

6 Summary

slide4

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

slide5

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

slide6

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 ??

slide7

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

slide8

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

slide9

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)

slide10

Contents

CBBI @PortlandSep. 8

1 Background

2 Objective

3 Synthesizing Li2+xTiO3+y

4 Crystal structure

5 Microstructure

6 Summary

slide11

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

slide12

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

slide13

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

slide14

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

slide15

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.

slide16

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.

slide17

Contents

CBBI @PortlandSep. 8

1 Background

2 Objective

3 Synthesizing Li2+xTiO3+y

4 Crystal structure

5 Microstructure

6 Summary

slide18

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.

slide19

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℃ 
slide20

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

slide21

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.

slide24

Quotation

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

slide25

Quotation

Li2MnO3

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

slide26

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