Hiroshi Nakatsugawa1, Masaki Kubota2 and Miwa Saito3
1Graduate School of Engineering, Yokohama National University, Yokohama 204-8501
In this study, polycrystalline samples of Pr1-xSrxMnO3 (0.1−≤ x−≤ 0.3) and La1-xSrxFeO3 (0.1−≤ x−≤ 0.3) were synthesized using a conventional solid-state reaction method. We investigated crystal structure, magnetic susceptibility (χ), and P-type thermoelectric properties, such as electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ), as a function of temperature (T) or Sr content (x). The perovskite structure at room temperature showed orthorhombic Pbnm phases for all samples. The samples for Pr1-xSrxMnO3 (0.1−≤ x−≤ 0.3) showed the ferromagnetic-like ground state below Curie temperature. Conversely, the samples for La1-xSrxFeO3 (0.1−≤ x−≤ 0.3) showed the antiferromagnetic-like ground state below Néel temperature. Although the samples for Pr1-xSrxMnO3 (x=0.1 and 0.2) showed a large positive S below room temperature, the carrier type changed from hole-like to electron-like behavior above 1000 K and 500 K, respectively. On the other hand, the samples for La1-xSrxFeO3 (0.1−≤ x−≤ 0.3) showed a large positive S over the whole temperature range. The largest dimensionless figure of merit (ZT) in the specimen for La0.7Sr0.3FeO3 was attaining a maximum value of 0.14 at 1000 K, by a decrease in both ρ and κ, and an increase in S. Recently, the coefficient of linear thermal expansion of La1-xSrxFeO3 has achieved the value which is equivalent to that of N-type CaMnO3. We expect that La0.7Sr0.3FeO3 is one of the candidate P-type materials for the oxide thermoelectric elements consisting of the same type of crystal structure.
thermoelectric properties, magnetic properties, perovskite structure, dimensionless figure of merit, Heikes formula
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