Effect of Na Addition on Electric Properties of Ca₂Si Sintered Compacts

Ca₂Si powders have been synthesized by the thermal treatment of Mg₂Si with NaI or Na₂CO₃ under Ca vapors, then sintered into compacts by sparking plasma sintering (SPS) technique. As a comparison, the compact was also sintered using Ca₂Si with NaI powders by the SPS technique. The effect of Na addition on the structural, transport and thermoelectric properties of the Ca₂Si compacts has been examined. All the samples show a p-type behavior in the measured temperature range. The Ca₂Si with Na₂CO₃ by vapor phase growth shows a higher carrier concentration of 1.28×10¹⁸ cm⁻³ conductivity about 10 times higher than Ca₂Si, and a power factor about 5 times higher than Ca₂Si from 350K to 570K.