ic502137m_si_001.pdf (1.53 MB)
NaCu6Se4: A Layered Compound with Mixed Valency and Metallic Properties
journal contribution
posted on 2014-11-17, 00:00 authored by Mihai Sturza, Christos
D. Malliakas, Daniel E. Bugaris, Fei Han, Duck Young Chung, Mercouri G. KanatzidisA new
ternary compound NaCu6Se4 was synthesized
from the reaction of Cu in a molten sodium polyselenide flux. The
compound crystallizes in trigonal space group R3̅m with a = 4.0465(3) Å and c = 41.493(5) Å. The crystal structure contains flat
two-dimensional slabs of 1/∞[Cu6Se4] with a unique structural arrangement, separated by
Na cations. The compound contains mixed valency and has a high conductivity
of ∼3 × 103 S cm–1 at room
temperature, and exhibits increasing conductivity with decreasing
temperature, indicating metallic behavior. A small positive thermopower
(4–11 μV K–1 from 300 to 500 K) and
Hall effect measurements indicate p-type transport with a carrier
concentration of ∼2.8(3) × 1021 cm–3 and a hole mobility of ∼8.75 cm2 V–1 s–1 at 300 K. NaCu6Se4 exhibits
temperature-independent Pauli paramagnetism.