High-Temperature Thermoelectric Properties of Pr_1−xSr_xFeO₃ (0.1 ≤ x ≤ 0.7)

Abstract

Polycrystalline specimens of Pr_1−xSr_xFeO₃ (0.1 ≤ x ≤ 0.7) were synthesized using a solid state reaction method. All samples had a typical perovskite structure, where the orthorhombic (Pbnm) phase was dominant at x ≤ 0.5 and the rhombohedral (R-3c) phase was dominant at x ≥ 0.6. Since the B site is in the mixed valence state of Fe³⁺/Fe⁴⁺ and the spin quantum number is in the range of 0.86 ≤ s ≤ 1.15, it is expected that Fe³⁺ is in the spin state of low spin (LS) Fe³⁺ or intermediate spin (IS) Fe³⁺ and Fe⁴⁺ is in the spin state of LS Fe⁴⁺. As x increases, the ratio of IS Fe³⁺ decreases compared to that of LS Fe³⁺ at x ≥ 0.3, so that the P-type Seebeck coefficient is maintained up to x = 0.5. Although ZT = 0.002 (T = 850 K) of x = 0.7 which shows the maximum N-type thermoelectric characteristic is about 8% of ZT = 0.024 (T = 850 K) of x = 0.1 which shows the maximum P-type thermoelectric characteristic, both are the results of relatively high Seebeck coefficient, low electrical resistivity, and low thermal conductivity. Therefore, we strongly suggest that there is a possibility of application of PN elements which compose of the perovskite-type oxides.

 

This Paper was Originally Published in Japanese in J. Thermoelec. Soc. Jpn. 15 (2018) 3–13.