Optimization of Bismuth Telluride Nanoparticles Synthesized via Spark Ablation

Nanoparticles are pivotal in advanced applications such as thermoelectric devices, sensors, solar cells and energy storage, owing to their increased surface area, enhanced phonon scattering, and reduced thermal conductivity. They are typically synthesized using high-temperature or wet chemical methods for larger sizes (∼100 nm), while smaller nanostructures (20 nm - 40 nm) are often achieved through solvothermal techniques, involving high temperatures and complex processes.
Our study focuses on applying a one-step spark ablation method to synthesize Bi₂Te₃ nanoparticles, aiming to optimize the diffusion parameters to produce high-purity nanoparticles with controllable sizes. Spark ablation is a simple, clean and versatile approach, ideal for producing thermoelectric materials. It requires only a base material and a carrier gas, resulting in a low-waste, rapid process that operates at room temperature without the need for complex equipment.
The spark ablation process involves ablation of two opposing metallic or semiconductor rods using repetitive high-voltage electrical sparks, which generate a supersaturated metal vapor in a carrier gas. This vapor rapidly condenses into nanoparticles, forming an aerosol of particles ranging from 2 nm to 20 nm in size. By producing several hundred sparks per second, a continuous nanoparticle flow is created and transported by an accelerated gas flow toward a target substrate for deposition.
Key parameters such as applied current, voltage, flow rate and ablation time are systematically varied to investigate their effects on the diffusion processes that govern nanoparticle growth and agglomeration. Through this methodical variation, the study aims to fine-tune the production process, ensuring optimal nanoparticle size and homogeneous distribution.
Through a series of experiments and comprehensive characterization techniques, including Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS), UV-Vis-IR Spectrophotometry, Raman spectroscopy and X-Ray Diffraction (XRD), we analyze the morphological, optical and structural properties of the produced nanoparticles. Our results reveal a strong correlation between the applied voltage and current and the produced nanoparticle size, while the carrier gas flow rate significantly impacts the homogeneity of both the nanoparticle dispersion and their agglomerates.
In conclusion, fine-tuning the spark ablation parameters effectively controls diffusion kinetics, leading to a tailored nanoparticle size range suitable for varied applications. Additionally, the spark ablation process enables direct deposition of nanoparticles onto any temperature sensitive substrate or prefabricated electronics.