実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report
課題番号 Project No.

提出日 Date of Report
装置責任者 Name of responsible person

2010B0012
実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Relationship between oxide-ion conductivity and ordering ofiMATERIA/(BL-20)

oxygen vacancy in the Ln2Zr2O7 (Ln = La, Nd, Eu) system

実施日 Date of Experiment

実験責任者名 Name of principal investigator

Dec. 13th, 2010

Takeshi Hagiwara
所属 Affiliation
Kanagawa university
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.

1) La2Zr2O7, sub micro-meter powder.
2) Nd2Zr2O7, sub micro-meter powder.
3) Eu2Zr2O7, sub micro-meter powder.

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.

Powder samples of Ln2Zr2O7 (Ln = La, Nd, Eu) were synthesized by a solid-state reaction
method, using ZrO2 (99.2%, Tosoh), La2O3 (99.99%, Wako), Nd2O3 (99.9%, Mitsuwa Chemicals),and Eu2O3 (99.9%, Mitsuwa Chemicals) as starting materials.
Weighed powders of starting materials were wet ball-milled for 20 h using a milling pot made ofsynthetic resin and resin-coated balls, and ethanol as a dispersion reagent. After drying, thepowder mixtures were calcined at 1373 K for 5 h in air.

The powder samples were molded

uniaxially under the pressure of 5 MPa and subjected to rubber press at 200 MPa, after sieving
under 53 μm in mesh size. Compacts thus obtained were sintered at 1873 K for 10 h in air.
These sintered samples were then crushed and ground into powder for submicron.
The neutron powder diffraction measurements were conducted in the IBARAKI Materirals
Design Diffractometer, iMATERIA, installed at the J-PARC. The neutron powder diffraction data
were collected with wide-d mode on the high resolution bank at room temperature. The collected
data were refined by Rietveld method using a cmputer program Z-Rietveld.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
The Pyrochlore-type structure belongs to a space group of Fd 3 m (Z = 8), where Ln3+ ions arelocated at the 16c site, Zr4+ ions at the 16d site, and O2- ions at the 8a and 48f sites. The 8b site isvacant in the completely ordered Pyrochlore-type structure. Therefore, the Rietveld analyses werecarried out assuming the following two structure-models: Model 1 was assumed to be a perfectpyrochlore structure, where the oxygen 8b site was vacancy, i.e. oxygen-8b site occupancy was fixed
to be 0.0, and Model 2 to be an oxygen-disordered pyrochlore structure, where the oxygen-8b site
was partially occupied by oxide-ions. Figure 1 shows the final results of the Rietveld analysis of
Nd2Zr2O7 on the basis of the two models. The Rwp values on the basis of model 1 and 2 were 7.39
and 6.37%, respectively. This fact shows that the Model 2 has higher reliability than the Model 1.
Therefore, we adopted the model 2 as the crystal structure model in this study.
Model 1

Rwp =7.39 %Rwp / Re = 1.79Model 2

Rwp =6.37 %Rwp / Re = 1.54

Figure 1 Rietveld analysis of Nd2Zr2O7 on the basis of two models.
Table 1 summarizes the results of Rietveld analysis for La2Zr2O7 and Nd2Zr2O7 according to theModel 2.
1)La2Zr2O7 : The 8a and 48f site occupancies were about 1.00.

Therefore, we suggested that

La2Zr2O7 had perfect pyrochlore structure and the 8b site occupancy was nearly 0.
2) Nd2Zr2O7 : As the 8a site occupancy was 1.00, the oxygen vacancy distributed between the 8b and48f sites.
3)Eu2Zr2O7 : We did not get the good fitting for Rietveld analysis because diffraction intensity of
Eu2Zr2O7 was very weak, although the collecting time of Eu2Zr2O7 was 10 times
comparing to that of the other samples. Therefore, The result of Eu2Zr2O7 (Figure 2)
was reference data.

22. 実験方法及び結果（つづき） Experimental method and results (continued)
Table 1 The results of Rietveld analysis of Ln2Zr2O7 (Ln = La, Nd)
La2Zr2O7AtomSiteOccupancyxyz

BLa

16c10.125

0.1250.1250.375(4)

Zr

16d

10.625

0.625

0.625

0.227(3)O18a1.000(2)0000.429(3)O28b0.023(2)

0.5

0.5

0.50.429(3)O348f

0.996(2)0.2936(1)000.429(3)Lattice parameter / nm 1.0812(1)Rwp = 5.87, Rwp / Re = 1.38, RB = 3.15, RF = 4.53

Nd2Zr2O7
AtomSiteOccupancy

xyz

B

Nd

16c

10.125

0.125

0.125

0.366(6)Zr

16d

10.625

0.625

0.625

0.705(7)O18a1.000(2)0000.862(6)O28b0.195(2)

0.5

0.5

0.50.862(6)O348f

0.967(1)0.2865(1)000.862(6)Lattice parameter / nm 1.0631(1)Rwp = 6.37, Rwp / Re = 1.54, RB = 4.52, RF = 8.55

Remarks: The isotropic atomic displacement parameters (B) of all oxide sites used the same value. And theoxygen 8b site occupancy is populating with concomitant of depopulation of the 48f site.

Rwp =6.40 %▼:Vanadium

Rwp / Re = 2.38▼▼ ▼Figure 2 Rietveld analysis of Eu2Zr2O7.
The results of this study can be summarized as follows :1) Rietveld analysis showed that the 8b site occupancy increased from 0.023 for La2Zr2O7 to 0.195
for Nd2Zr2O7. The increase in 8b site occupancy means the increase of disordered oxide-ion in the
pyrochlore structure.
2) The oxide-ion conductivity increased with an increase in the 8b site occupancy which can berecognized as a measure of disordered oxide-ion in the pyrochlore-type structure.

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