Growth of anodic aluminum oxide templates and the application in fabrication of the BiSbTe-based thermoelectric nanowires

A two-step electrochemical anodization was used to form the anodic aluminum oxide (AAO) thin films with nanotube arrays of self-organized honeycomb structure. Al foil was anodized in 10% sulfuric acid (H₂SO ₄) and 3% oxalic acid (H₂C₂O₄) at 25°C at constant voltage of 40 V for 60 min for two times. Ethylene glycol (C₂H₆O₂) was used as a solution and 0.3 M potassium iodide (KI) was used to improve the solution's conductivity. Different electrolyte concentrations of Bi(NO₃)₃-5H₂O, SbCl₃, and TeCl₄ were added into KI-C₂H ₆O₂ solution and the cyclic voltammetry experiment was used to find the reduced voltages of Bi³⁺, Sb³⁺, and Te⁴⁺ ions. The potentiostatic deposition and pulse electrodeposition (PED) processes were used to deposit the (Bi,Sb)_2-xTe _3+x-based materials. Field-emission scanning electron microscope and energy dispersive spectrometers were used to analyze the compositions of the deposited (Bi,Sb)_2-xTe_3+x-based materials. After finding the optimal deposition parameter of the PED process the AAO nanotube arrays were used as the templates to deposit the (Bi,Sb)_2-xTe _3+x-based thermoelectric nanowires.