Investigation of Phase Transition from Critical Nucleus to Bi2Te3 Nanoplate Based on Screw Dislocation‐Driven Spiral Growth by Solvothermal Synthesis

Two‐dimensional bismuth telluride (Bi2Te3) nanoplates have great potential for thermoelectrics and topological insulators. The material performance increases as the nanoplate size decreases. However, the initial stage of the crystal growth of the nanoplates has not been significantly investigated. The Bi2Te3 nanoplates are prepared by solvothermal synthesis and the phase transition based on the screw dislocation‐driven spiral growth of the nanoplates is investigated. The optimal synthesis conditions are first determined by controlling the Te concentration in the precursor solution. The spiral‐grown nanoplates are collected from the synthesized products. The diameter of the critical nucleus is calculated to be in the range of 5.0–7.2 nm from the step width in the spiral. Subsequently, the solvothermal synthesis is implemented by changing the synthesis time from 15 to 1200 min under the optimal conditions of the precursor solution. Crystals are not grown in the solution at 15 min. At 25 min, an intermediate phase of Bi2TeO5 with an approximate grain size of 5.0 nm is formed, which corresponds to the calculated diameter of the critical nucleus. Another intermediate phase of Te is formed, and the Bi2Te3 nanoplates with a lateral size of 300 nm grow slowly at the expense of Bi2TeO5 and Te.