Isovalent Ca and Ba substitutions in thermoelectric layer-structured oxyselenide Sr2CoO2Cu2Se2

T. L. Chou, O. Mustonen, T. S. Tripathi, M. Karppinen*

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    5 Citations (Scopus)

    Abstract

    Multilayered compounds typically present exotic functionalities, and some of them have been suggested as potential materials for thermoelectric conversion owing to their unique capability to decouple electronic and heat transport. Here we report new [CoO2] and [Cu2Se2] layered A(2)CoO(2)Cu(2)Se(2) compounds in which Sr at the intervening alkaline-earth A site is partially replaced with Ca or Ba. The parent Sr2CoO2Cu2Se2 phase is a direct gap p-type semiconductor, and density functional theory (DFT) calculations indicate its topmost valence band consists of Cu 3d-Se 4p states. Upon the isovalent cation substitution the lattice modification in the ab plane is constrained by the stiff [CoO2] layer such that the lattice shrinkage/expansion mainly happens along the c axis. Substitution of Sr with the heavier and larger Ba significantly enhances the thermopower but more hole states would be required to optimize the thermoelectric performance. Thermal stability is related to the inter-oxide-selenide-layer interaction, and our thermogravimetric measurement data reveal that the A(2)CoO(2)Cu(2)Se(2) materials could operate in the intermediate temperature region.

    Original languageEnglish
    Article number035802
    Number of pages7
    JournalJournal of physics: Condensed matter
    Volume28
    Issue number3
    DOIs
    Publication statusPublished - 27 Jan 2016
    MoE publication typeA1 Journal article-refereed

    Keywords

    • thermoelectrics
    • layered structure
    • chemical pressure
    • electronic structure
    • DENSITY-FUNCTIONAL THEORY
    • CRYSTAL-STRUCTURE
    • ELECTRONIC-PROPERTIES
    • BICUSEO OXYSELENIDES
    • MAGNETIC-PROPERTIES
    • PERFORMANCE
    • OXYCHALCOGENIDES
    • OXYSULFIDES
    • SR
    • SE

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