Thermoelectric properties of Ba<inf>8</inf>Al<inf>16</inf>Si<inf>30</inf> Clathrate

Abstract

Clathrate Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> was produced by arc melting and hot-pressed and effects on the microstructure and thermoelectric properties were investigated. The ingot was crushed into powders in a glove box. The powders were hot-pressed at 1,073, 1,123 and 1,173K using a stress of 60 MPa for 2 hours. The phase transformation behavior of hot-pressed Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> was examined by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), hardness test, X-ray diffraction and scanning electron microscope analyses. Seebeck coefficient (thermoelectric power), Thermal conductivity, Dimensionless-figure-of-merit (ZT), electrical conductivity and thermoelectric power factor were investigated from room temperature to 600 K. The hot-pressed and isothermal homegenized specimens represented n-type conduction at temperatures examined. Thermoelectric properties are compared hot-pressed samples to as-solidified and homogenized samples. Hot-pressed at 1,173 K using a stress of 60 MPa for 2 hours sample shows good thermoelctric properties at this examined conditions.