Insight into Nucleation and Growth of Bi_2–xSb_xTe₃ (x = 0–2) Nanoplatelets in Hydrothermal Synthesis

Abstract

Controlled wet chemical synthesis of nanomaterials with tailored structures and properties, especially by hydrothermal/solvothermal methods, is difficult due to the complicated nucleation and growth processes. Therefore, it is important to gain a deeper understanding of the formation mechanisms involved in hydrothermal/solvothermal processes. In the present study, the formation mechanisms of Bi2-xSbxTe3 (x = 0-2) nanoplatelets under hydrothermal conditions are studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXRD). Synthesis using glucose as the reducing agent results in direct nucleation of Bi2Te3 from Bi and Te precursors without the presence of any intermediate products, and the nucleation stage is completed in only about 1 min at 250 °C. When Sb is added the nucleation process for Bi2-xSbxTe3 becomes slower with increasing Sb content.Depending on the Sb content and reaction temperature, an intermediate product of elemental Te nanostructures forms, and it is found to direct the morphology of the final products. Within the duration of the measurements, Sb2Te3 only forms at relatively high reaction temperatures due to the slower kinetics of the reaction. A two-stage nucleation mechanism is found for the formation of the ternary BiSbTe3 with an initial nucleation stage of predominately Bi2Te3 followed by a second stage of slower 2 nucleation and alloying process to BiSbTe3. Both the composition and reaction temperatures affect the crystallization kinetics and crystallite growth mechanisms during synthesis of Bi2-xSbxTe3 nanoplatelets.

Into the Void: Single Nanopore in Colloidally Synthesized Bi2Te3 Nanoplates with Ultralow Lattice Thermal Conductivity

“…Other interpenetrating nanorod with nanoplate morphologies have been observed in Bi 2 Te 3 , Bi 2 Se 3– x Te x , and Bi 2– x Sb x Te 3 materials. 50 − 52 As the reaction progresses, the Te nanorod is consumed, and the Bi 2 Te 3 nanoplate grows epitaxially, as seen at 2 ( Figure 2 b), 3 ( Figure 2 c), and 4 h ( Figure 2 d). At 5 h, most of the Te nanorods have detached from the plates, leaving some with a pore and some still containing a Te rich core ( Figure 2 e).…”

In Situ Characterization of Transformations in Nanoscale Layered Metal Chalcogenide Materials: A Review

“…Beyond influencing grain growth mechanisms, metal atoms can also alter crystallization kinetics through the formation of different intermediate phases which further transform to produce the desired layered MC structure. In situ XRD analysis was performed by Mi et al [64] to observe the role of Sb 3 + ions during Bi 2 Te 3 crystallization. As shown in Figure 4a, Bi 2 Te 3 nanoplatelets form as the Bi 3 + and TeO 3 2À ions readily react at 200°C without the formation of any intermediate phases.…”

“…Schematic illustration of the formation mechanisms of a) Bi 2 Te 3 nanoplates and b) Bi 2Àx Sb x Te 3 nanostrings upon addition of Sb 3 + ions. Reproduced with permission from Ref [64]…”

A Flow-Through Reaction Cell for Studying Minerals Leaching by In-Situ Synchrotron Powder X-ray Diffraction

“…There are a number of in-situ techniques, capable of studying the solution phase by X-ray absorption spectroscopy [12] and Raman spectroscopy [13], and solid phase by transmission electron microscopy [14], atomic force microscopy [15], neutron diffraction [16][17][18], and powder X-ray diffraction (PXRD) [19][20][21][22]. In-situ PXRD in the presence of an aqueous solution can reveal the phase evolution of the crystalline materials and has been applied extensively in materials chemistry for elucidating crystallization mechanisms of hydrothermal materials syntheses [23][24][25][26][27][28]. This technique has also been applied in studying mineral leaching, but mostly under static conditions using glass capillary tubes [8][9][10][11].…”