Thermoelectric properties of Ca-Ir-O compounds prepared by spark plasma sintering

Nittaya Keawprak, Rong Tu, Takashi Goto

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Ca-Ir-O Compounds in various molar ratios of Ir to Ca (RIr/Ca) from 0.2 to 1.2 were synthesized by solid-state reaction and compacted by spark plasma sintering (SPS). Ca4IrO6 and CaIrO3 with a small amount of second phase were obtained at RIr/Ca = 0.25 and 1.0, respectively, whereas Ca2IrO4 in a single phase was obtained at RIr/Ca = 0.5. The electrical conductivity was 4 × 10-4 to 150 Sm-1 at room temperature and exhibited a semiconducting behavior for all the samples. The Seebeck coefficient at R Ir/Ca = 0.4 to 0.7 showed negative values whereas samples with R Ir/Ca = 0.25 and 0.9 to 1.2 showed positive values. The thermal conductivity was 1.1 to 2.7 Wm-1K-1 at room temperature and slightly decreased with increasing temperature. The highest ZT value of p-type was 0.006 at 1023 K and RIr/Ca = 11 and 1.2, while that of n-type was 0.0022 at 800 K and RIr/Ca = 0.5.

Original languageEnglish
Pages (from-to)853-858
Number of pages6
JournalMaterials Transactions
Issue number4
Publication statusPublished - 2009 Apr


  • Calcium iridium oxide
  • Spark plasma sintering
  • Thermoelectric materials

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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