Thermoelectric properties of Ca_(1-x)Sr_xRuO_3 compounds prepared by spark plasma sintering

摘要

Single phase Ca_(1-x)Sr_xRuO_3 (x=0-1.0) powders were synthesized by a solid-state reaction and compacted by spark plasma sintering. The a-length of the lattice parameter showed a slight minimum around x - 0.6, whereas the b-length, c-length and the unit cell volume increased continuously with increasing x from 0 to 1.0, indicating a solid solution in the whole range. The relative density of Ca_(1-x)Sr_xRuO_3 compacted bodies increased from 75 to 95% with increasing x from 0 to 1.0. The electrical conductivity (σ) at x=0.1-0.9 was higher than those of the end members (CaRuO_3 and SrRuO_3) except for that at x=0.5, and showed metallic conduction at all compositions. The Seebeck coefficient (S) was 30-40 μV K~(-1), almost independent of composition and temperature. The thermal conductivity (/c) was 2-3 Wm~(-1) K~(-1) at room temperature and increased with increasing temperature. The k showed the lowest values at x=0.2 in the whole temperature range. The dimensionless figure-of-merit (ZT) at x=0.1-0.9 was higher than those of the end members. The highest ZT was 0.07 at x = 0.2 and 600 K.