実験報告書様式（一般利用課題・成果公開利用）

MLF	 Experimental Report

提出日 Date of ReportFebruary 3, 2015.

課題番号 Project No.

装置責任者 Name of responsible person

2014A0290

Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）µ+SR study for oxygen-ion diffusion in solids

D1

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Jun Sugiyama

November 22, 2014 - November 23, 2014

所属 Affiliation
Toyota Central Research and Development Laboratories, Inc.
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
Lithium iron manganese phosphate LiFe0.5Mn0.5PO4, LiFe0.2Mn0.8PO4 and LiFe0.1Mn0.9PO4.
A powder sample was packed into a gold o-ring sealed titanium cell.

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

Originally, we planned to measure µSR spectra for oxygen-ion conducting materials at high temperatures until
1273 K using an oven heated with an infrared lump (proposal #2014A0290). However, due to the upgrade of thespectrometer of D1, the size of the sample space was significantly changed. As a result, such oven wasunavailable in 2014. Therefore, we measured a diffusive nature of lithium iron manganese phosphates(LiFe1-xMnxPO4) up to 400 K using a liquid He flow-type cryo-oven (proposal #2014B0266).
According to our µSR study on LiMnPO4 [1], the ZF-spectrum was found to show a rapidly relaxing behavior
due to large magnetic moments of Mn2+ ions (S=5/2) even at 300 K. This means that it is difficult to know thediffusive behavior in LiMnPO4, because a Kubo-Toyabe-type relaxation caused by nuclear magnetism of Li
was entirely hindered by the rapid relaxation. We have, thus, attempted to measure µSR spectra of a solid
solution system between LiFePO4 and LiMnPO4 in order to extrapolate the diffusive nature of LiMnPO4 fromthe result of LiFe1-xMnxPO4.
Powder samples of LiFe0.5Mn0.5PO4, LiFe0.2Mn0.8PO4 and LiFe0.1Mn0.9PO4 were prepared by a conventional
solid-state reaction technique. Then, each powder sample (about 1 g) was packed into a titanium cell sealedwith a gold O-ring. The window of the Ti cell was a Kapton film with 100 µm thickness.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
with a gold O-ring. The window of the Ti cell was Kapton
foil with 100 µm thickness.

0.2
LiFe0.5Mn0.5PO4

for LiFe0.5Mn0.5PO4 obtained at 100 and 300 K. Although
the spectra indicate a static nature at 100 K, theA0P(t)Figure 1 shows ZF- and two LF-spectra (5 and 10 Oe)

0.1

internal field becomes dynamic at 300 K. The spectra
were well fitted by a combination of a dynamic

LF 10Oe
LF 5OeZF(a) T=100K

LF 10Oe
LF 5OeZF(b) T=300K

00.2

Kubo-Toyabe signal due to Li-diffusion [1,2,3,4], an
early time domain, and time-independent backgroundsignal from the muons stopped in the Ti cell.
Figure 2 shows the temperature dependences of theA0P(t)exponential relaxation signal due to Mn moments in an0.1

field distribution width (Δ) and field fluctuation rate (ν)

00for the three samples. For the x=0.5 sample, theincrease in ν above 200 K is not so drastic, while ν forthe x=0.8 sample clearly increases with increasing
temperature until 325 K. A similar behavior is also

510TIME (µs)

15Fig. 1 ZF- and two LF-µSR spectra (5 and 10 Oe)
for LiFe0.5Mn0.5PO4 obtained at 100 and 300 K.

observed for the x=0.9 sample, although we have the0.5

implies that Li-diffusion in LiFePO4 is enhanced by the0.4

Mn-substitution for Fe. This is consistent with the-1

prediction from first principles calculations [5]; namely,6" (10 s )data only below 300 K due to a limited beam-time. Thisa diffusion coefficient (DLi) for LiMnPO4 is predicted as
10-7 cm2/s, while DLi for LiFePO4 10-8 cm2/s.

LiFe1-xMnxPO4(a)

0.3
0.2
0.1

x=0.9
x=0.8
x=0.5

02-1
6

[1] J. Sugiyama et al., Phys. Rev. B 85, 054111 (2012).
[2] J. Sugiyama et al., Phys. Rev. Lett. 103, 147601(2009).
[3] M. Mansson and J. Sugiyama, Physica Scripta 88,068509 (2013).
[4] J. Sugiyama et al., Phys. Rev. B 84, 054430 (2011).
[5] D. Morgan et al., Electrochem. Solid-State Lett. 7,A30 (2004).

! (10 s )REFERENCES(b)

1.5
10.5
00

x=0.9
x=0.8
x=0.5

100 200 300 400 500
TEMPERATURE (K)Fig. 2 T dependences of (a) the field distribution
width (Δ) and (b) field fluctuation rate (ν) for
LiFe1-xMnxPO4 with x=0.5, 0.8, and 0.9.

2