Study of Lithium Titanate with excess Li for an advanced tritium

Report
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
[email protected]
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

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