F3-13-O25
Materials Research Meeting 2019
December 10-14, 2019, Yokohama, Japan

Thermoelectric properties of (Pr, Nd, Sm)1-xSrxFeO3 (0.1≤ x ≤0.5) oxides
Hiroshi Nakatsugawa1,*, Shunta Kazama1, Miwa Saito2, Yoichi Okamoto3
1Yokohama National University, Yokohama, 240-8501, Japan,
2
Kanagawa University, Yokohama, 221-8686, Japan,
3
National Defense Academy, Yokosuka, 239-8686, Japan*naka@ynu.ac.jp (Corresponding author)
Keywords: Fe-oxides, electric resistivity, Seebeck coefficient, thermal conductivity, figure of merit
Recently, oxide material has attracted much attention as a candidate for thermoelectric (TE) conversion
material. Among oxides having a perovskite structure, in particular, Nb-doped SrTiO3 1), Ca1-xAxMnO3(A=Yb,Tb,Nd,Ho) 2), La1-xSrxFeO3 3), La1-xSrxCoO3 4) and so on are reported as oxides which show relatively
large Seebeck coefficient S. These large S is the result of strong interaction of the spin state, orbital, charge, andcrystal structure of the 3d transition metal element. It is expected that the TE properties of 3d transition metaloxide can be controlled by considering the spin state of 3d electrons in the transition metal ions. We focused on
the Fe-oxide with perovskite structure showing P-type and N-type TE characteristics. In this study, thepolycrystalline sample of (Pr, Nd, Sm)1-xSrxFeO3 (0.1≤ x ≤0.5) was fabricated, and the correlation between thecrystal structure, the magnetic properties and the TE characteristics was clarified by considering the spin state ofFe ions in the Fe-oxides. As shown in Fig.1, we exhibited the P-type TE properties and found that Pr0.9Sr0.1FeO3shows ZT=0.024 at T=850K which is the best of the P-type TE characteristics of Pr1-xSrxFeO3 (0.1≤ x ≤0.5) 5). If
we can realize the low spin or the intermediate spin states of Fe3+ by partially replacing Sr2+ having a smaller
ionic radius than Pr3+ and releasing the chemical pressure applied to Fe ions by precisely controlling the Fe-O
distance and the Fe-O-Fe angle, it is possible to realize both the P-type and the N-type TE characteristics. As
shown in Fig.2, we exhibited both the P-type and the N-type TE properties and found that Nd0.9Sr0.1FeO3 andNd0.5Sr0.5FeO3 show ZT=0.008 at T=850K and ZT=0.002 at T=850K which are the best P-type and the N-type TE
characteristics of Nd1-xSrxFeO3 (0.1≤ x ≤0.5), respectively. Thus, it suggests that a PN element for hightemperature TE materials can be possible to construct using only Fe-oxides having the perovskite structure.
4000.02

4000.02−1300

S / VKS / VK−1300

200

100

ZTZT

1002000.01

00.01
200300400500

T/K600700200800

400300

Nd1−xSrxFeO3Pr1−xSrxFeO3x = 0.1
x = 0.2x = 0.3x = 0.4x = 0.5

0300

0400

500

T/K

600

700

800

x = 0.1x = 0.2x = 0.3x = 0.4x = 0.5

500

600
T/K

700

800

Fig. 1. Temperature dependence of ZT for Pr1-xSrxFeO3 (0.1≤ x ≤0.5),
where the inset shows temperature dependence of S.

0300

400

500

600

700

800

T/K
Fig. 2. Temperature dependence of ZT for Nd1-xSrxFeO3 (0.1≤ x ≤0.5),
where the inset shows temperature dependence of S.

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