Influence of laser treatment on the thermoelectric properties of bismuth telluride material

In this research the impact of laser processing (LP) on the thermoelectric (TE) characteristics of bismuth antimony telluride (BST) alloy pellets is investigated. This innovative approach examines how varying LP parameters can influence TE properties by selectively modifying the outer layers of the material through a process involving melting and solidification. The stoichiometric alloy used is Bi 0.4 Sb 1.6 Te 3.0 , which was prepared by mechanical alloying techniques (MA) and hot pressed (HP) into pellets under optimal pressing and temperature conditions. The LP process was executed by employing a metal 3D printer, with a thorough analysis of beam parameters. Notably, the laser power (P) was held constant at 25 W, along with a fixed hatching distance (HD) of 50 mu m, while the parameter adjusted was the laser's scanning speed (SS), which spanned from [600-1800] mm/s in increments of 200 mm/s. Examination via scanning electron microscopy (SEM) revealed two material states: melted and sintered. The melted state formed the surface crust of "canyon"patterns that were held on the surface of the samples, and which both size and quantity were altered with changes in SS. For thermoelectric characterization, two distinct shapes of LP samples were produced: rectangular (for electrical properties) and disk (for thermal properties). The results demonstrated that the electrical properties are profoundly influenced by SS, with the electrical conductivity peak at SS value of 1600 mm/s, while the Seebeck coefficient reaches a minimum at the same value. Consequently, within the temperature range of interest, a notable 12% increase in electrical conductivity and a 9% decrease in the Seebeck coefficient were observed compared to the non-LP material state. Overall, the ZT value experience an 6.9% decline within the same temperature interval.