Due to its nontoxicity, suitable bandgap, high defect tolerance and high electron mobility, layered BiI 3 has been gaining attention in photoelectric device and nonlinear optics field. However, the growth of large-size single crystal 2D BiI 3 has not been achieved. Herein, the synthesis of single crystal 2D BiI 3 on mica substrate via a cooling-induced growth method is reported, with the thickness of 8 ∼ 1000 nm and a lateral dimension of 110 ∼ 1000 μm. X-ray diffraction and selected area electron diffraction demonstrate the single crystal nature of 2D BiI 3 flakes. The high temperature during heat preservation step prevents the deposition of BiI 3 vapor, and then, when proceeding to cooling-induced growth step, single crystal 2D BiI 3 flakes start to nucleate on colder mica substrate and grow up to ∼ 1000 μm (lateral dimension) rapidly. The stability test indicates the 2D BiI 3 flake decomposes with the present of both O 2 and water. Finally, the cooling rate, height of crucible, holding temperature and type of substrate have also been investigated to show the structural evolution of 2D BiI 3 flakes.
Single crystals of three new organic–inorganic hybrid compounds, tri[1-(diaminomethylene)uronium] hexachlorobismuthate ((C 2 H 7 N 4 S) 3 BiCl 6 ·H 2 O, HATU-BCH), bis[1-(diaminomethylene)uronium] pentabromobismuthate, ((C 2 H 7 N 4 S) 2 BiBr 5 , HATU-BB), and bis [3,5-diamino-1,2,4-thiadiazol-2-ium] pentaiodobismuthate ((C 2 H 5 N 4 S) 2 BiI 5 , OHATU-BI), have been successfully grown by slow evaporation method. Their structures were determined by single - crystal X-ray diffraction, in which all anion sublattice structures consist of hexahalobismuthates octahedra with different connection modes involving isolated, shared-corner, and shared-edge. The spectra characters were studied by Infrared and Raman spectra, which interpreted by calculation of the density functional theory (DFT) method and diffuse reflectance spectra. Thermal properties were characterized by thermal gravimetric analysis and differential scanning calorimetry.
The single crystal growth of Mg 3 Bi 2 -based thermoelectric materials is of great significance for their applications near room temperature. So far, it is still a big challenge to grow such bulk single crystals and attempts are primarily focused on the metal flux methods. For the first time, bulk single crystals of n-type Mg 3 Bi 1.49 Sb 0.5 Te 0.01 are directly grown by applying an In-situ Loading Bridgman method. The as-grown single crystal features an excellent carrier mobility of 220 cm 2 V −1 s −1 , which is among the best compared to other Mg 3 Bi 2 -based bulk materials. Besides, this method is successfully developed to fast grow uniform polycrystalline materials with high thermoelectric and mechanic performance. As demonstrated by the single-leg device, a large temperature difference of 10.5 K is achieved at the supplied electric current of 0.6 A, much superior to other room temperature state-of-the-art thermoelectric materials. With the single crystalline and polycrystalline materials prepared reliably and conveniently, in-depth investigations on the Mg 3 Bi 2 thermoelectric system can be greatly benefited, which should as well significantly facilitate their practical applications at room temperature.
危险品化学品经营许可证（带存储）