Estudo dos compostos Half Heusler NbFeSb, TiCoSb e NbCoSb

Abstract

Heusler compounds are a class of materials with 1:1:1 or 2:1:1 stoichiometry. HalfHeusler compounds have a 1:1:1 stoichiometry, while the Heusler or Full Heusler compounds have a 2:1:1 stoichiometry. Half-Heusler compounds have attracted attention due to thermoeletric properties and Full Heusler compounds for magnetic properties. We report on the structural, eletrical, and thermal properties of NbFeSb, NbCoSb and TiCoSb synthesized by Mechanical Alloying. X-ray difraction data of the phase transformations during the mechanical alloying were collected and analyzed. A single-phase, Half-Heusler allow was successfully produced by the mechanical alloying process for NbCoSb and TiCoSb, but a minor portion of the secondary phase was observed after the mechanical alloying process for NbFeSb. The structural stability of the samples were evaluated for Differential Scanning Calorimetry. Thermal conductivity was evaluated from the measurements of thermal diffusivity, specific heat and density obtained by thermal-conductivity analyzer (TCI) equipament. The evolution of its structural and thermal characteristics were investigated by Rietveld method. The calculated lattices constants is in good agreement with the available experimental data in literature. Tha band structure and density of states are obtained from density functional theory and spectroscopy Ultraviolet Visible. The phase produced by mechanical alloying process will showed much low thermal conductivity values after a mechanical alloying.