Zhengliang Sun

A general strategy to bismuth chalcogenide films by chemical vapor transport

Developing a low-cost, simple manufacturing process for highly efficient thermoelectric films is an intriguing topic for both chemists and materialists. In this work, a new strategy was introduced to synthesize bismuth chalcogenide films by chemical vapor transport on presynthesized Bi films, including Bi2Se3, Bi2Te3 and Bi2Te2.7Se0.3. Through delicate control of the chalcogen vapor pressure, highly qualified and (00l) oriented bismuth chalcogenide films, constructed by oriented nanoplates, were obtained. The (00l) orientation of the films will facilitate the transport of the carrier for bismuth chalcogenides. Thermoelectric properties of these films were also characterized. At room temperature, the power factors reach 3 μW cm−1 K−1, 18.7 μW cm−1 K−1, 24.6 μW cm−1 K−1 for Bi2Se3, Bi2Te3, Bi2Te2.7Se0.3 films, respectively. Besides, the average power factor of 31.2 μW cm−1 K−1 in the temperature range of 300–500 K for Bi2Te2.7Se0.3 films indicates the present chemical vapor transport process is a promising technique for thermoelectric films.

Enhanced Thermoelectric Properties of Bi0.5Sb1.5Te3 Films by Chemical Vapor Transport Process

Bi₀.₅Sb₁.₅Te₃ films were prepared by a novel chemical vapor transport process through delicate controlling the temperature of the substrate and vapor source. The power factor reaches 30 μW cm⁻¹ K⁻¹ at room temperature, which is much higher than the value of the Bi₀.₅Sb₁.₅Te₃ films prepared by other techniques. The enhancement of thermoelectric properties might be attributed to the higher carrier mobility (252 cm² V⁻¹ s⁻¹), coming from the effective interparticle contiguity of (00L) oriented nanoplates embedded in the present Bi₀.₅Sb₁.₅Te₃ films.

Enhancing thermoelectric performance of bismuth selenide films by constructing a double-layer nanostructure

A new nanostructure of double-layer thin films (DLTFs) has been introduced to Bi2Se3 as thermoelectric films through a facile one-step and low-temperature solution route. The Bi2Se3 DLTFs consist of a (001) orientational inner layer and a (110) orientational outer layer with controllable thicknesses. The controllable release of the precursor ion is critical to adjust the double-layer nanostructures. The maximum power factor of the Bi2Se3 DLTFs reaches 100 μW m−1 K−1, which is larger by 79% than the value for a single layer Bi2Se3 film.

Topotactic synthesis of alternately stacked Ca3Co4O9/γ-Na0.66CoO2 composite with nanoscale layer structure

A novel process has been introduced to synthesize an alternately stacked Ca3Co4O9/γ-Na0.66CoO2 composite with nanostructured layers and high c-axis orientation. The thickness of each layer is about 60–100 nm. The maximum power factor at 1000 K is 6.3 × 10−4 W m−1 K2, which is about 50% higher than that of conventional Ca3Co4O9 ceramics.