Crystal cluster growth and physical properties of the EuSbSe3 and EuBiSe3 phases.

Syntheses of europium metal, selenium powder, and the Sb(2)Se(3)/Bi(2)Se(3) binaries were observed to produce crystal clusters of the EuSbSe(3) and EuBiSe(3) phases. These phases crystallize with the P2(1)2(1)2(1) space group and can be easily identified based on their growth habits, forming large clusters of needles. Previous literature suggested that their structure is charge-balanced with all europium atoms in the divalent state and one-quarter of the selenium atoms forming trimers. Physical property measurements on a pure sample of EuSbSe(3) revealed typical Arrhenius-type electrical resistivity, being approximately 3 orders of magnitude too large for thermoelectric applications. Electronic structure calculations indicated that both EuSbSe(3) and EuBiSe(3) are narrow-band-gap semiconductors, in good agreement with the electrical resistivity data. The valence and conduction band states near the Fermi level are dominated by the Sb/Bi and Se p states, as expected given their small difference in electronegativity.