Abstract
Doped BiCuSeO is one of the promising thermoelectric oxide candidates. However, the research on doping effects on the electrical transport properties of BiCuSeO, especially in crystalline samples, is still limited. Here, we studied the transport properties of doped BiCuSeO crystals, including three types of doping species (Rb, Sn, and Co) with varying concentrations. In the case of Rb-doped BiCuSeO crystals, few percentage (≤1%) Rb-doping make BiCuSeO display metallic behavior, while high one (≥2%) displays bad-metallic behavior. Both Sn- and Co-doped BiCuSeO crystals have similar electrical evolution as Rb-doped ones. The charge carriers of all these doped BiCuSeO crystals are holes, and the increased dopant concentration decreases the hole concentrations regardless of the type of dopant species. There is negative magnetoresistance (MR) in Rb- and Sn-doped BiCuSeO at low temperature (<15 K), which is due to the breakdown of weak localization by magnetic field B, but the MR behaviors in Co-doped BiCuSeO crystals are strongly correlated with their magnetic properties. The analysis of the temperature-dependent mobility of these doped BiCuSeO crystals substantiates that at low temperatures (<50 K), electron-impurity scattering dominates, while electron–phonon scattering dominates at high temperatures (>50 K). The evolution of the above-mentioned electrical/magneto-transport properties of doped BiCuSeO can be understood as follows: the dopant compensates the Bi-deficiency in pristine BiCuSeO crystals and decreases the hole concentration and leads to the metal–Anderson-insulator transition. These results may be valuable to optimize the electrical properties of layered compounds similar to BiCuSeO.
Highlights
BiCuSeO oxyselenide is a potential thermoelectric (TE) material because of its quite low lattice thermal conductivity [κL ∼ 1 W/(m K)] and relative large Seebeck coefficient (α > 300 μV/K).1–5These properties are mainly due to its quasi-two-dimensional crystal structure where nately stacked withBiCuSeO (Bi2O2)2+is formed by (Cu2Se2)2− layers layers.6 according to alterpreviously published papers, BiCuSeO has a low electrical conductivity of σ ∼ 2.5 S/m at room temperature,7 which is a key factor limiting its TE conversion efficiency
There is negative magnetoresistance (MR) in Rb- and Sn-doped BiCuSeO at low temperature (
The lowest doped BiCuSeO has the electrical feature of degenerate semiconductors
Summary
BiCuSeO oxyselenide is a potential thermoelectric (TE) material because of its quite low lattice thermal conductivity [κL ∼ 1 W/(m K)] and relative large Seebeck coefficient (α > 300 μV/K).. An effective way to improve the electrical conductivity of BiCuSeO is to increase the carrier concentration by doping.. Based on these efforts, the electrical conductivity of BiCuSeO increases to 8.88 × 104 S/m at 300 K.18. The doping mechanisms in doped BiCuSeO and the doping effect on its electrical transport properties are still quite unclear because the samples used in the above-cited works are based on polycrystals. Scitation.org/journal/adv extension is if we dope BiCuSeO by foreign elements, what are the effects of foreign elements on the electrical transport properties of BiCuSeO crystals?. We have grown a series of Rb-, Sn-, and Co-doped BiCuSeO crystals to explore the effect of foreign dopants on their electrical transport properties. We characterized the temperature-dependent resistivity and magnetoresistance (MR) of these crystals and further summarized the generic electrical- and magneto-transport properties of doped BiCuSeO
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