Papers by Author: Mei Jun Yang

Abstract: The single phase of Bi-doped Mg2Si0.5Sn0.5 compounds have been successfully fabricated by solid state reaction-spark plasma sintering (SPS). The effect of Bi doping concentration on the thermoelectric properties of Mg2Si0.5Sn0.5 is mainly investigated. The doping of Bi atom introduces impurity energy to Mg2Si0.5Sn0.5 compounds, which results in the increase of carrier concentration ( ), meanwhile it causes the increase of crystal distortion, enhancing the scatter of phonon. The results show that with the increasing of Bi doping content, the electrical conductivity (σ) increase, the absolute Seebeck coefficient ( ) and thermal conductivity ( ) decrease slightly in the measuring temperature range between 300 K and 800K. When the doping concentration of Bi is up to 2.5at% (nominal molar percent), the sample shows a maximum value of the figure of merit, ZT, is 0.78 at 800K.

Abstract: Nanocomposites and heavy doping both are regarded as effective way to improve materials’ thermoelectric properties. 0.7at% Bi-doped Mg2Si nanocomposites were prepared by spark plasma sintering. Results of thermoelectric properties tests show that the doping of Bi atom effectively improves the electrical conductivity of Mg2Si，and the nanocomposite structures are helpful to reduce thermal conductivity and increase Seebeck coefficient, hence improving the thermoelectric performance. A maximum dimensionless figure of merit of 0.8 is obtained for the Bi-doped Mg2Si nanocomposite with 50 wt % nanopowder inclusions at 823K, about 63% higher than that of Bi-doped Mg2Si sample without nanopowder inclusions and 119% higher than that of microsized Mg2Si sample without Bi-doped, respectively.

Abstract: SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal expansion (CTE), were characterized. High relative density (R-D) of composites was successfully achieved through the optimization of sintering parameters, such as sintering temperature, sintering pressure and heating rate. The measured TCs of SiCp/Al composites fabricated by SPS are higher than 195W/m.k, no matter the volume fraction of SiC particles is high or low as long as the R-D is higher than 95%. The measured CTEs of SiCp/Al composites are in good agreement with the estimated values based on Kerner,s model. The high volume fraction of SiCp/Al composites are a good candidate material to substitute for conventional thermal management materials in advanced electronic packages due to its tailorable thermophysical properties.