Thermoelectric properties of higher manganese siliicide compounds synthesized by MG-PDS Method

Abstract

Higher manganese suicide (HMS) is a candidate for the low-cost and environment-friendly thermoelectric materials available to the thermoelectric power generation recovering waste heat. In this study, we synthesized HMS compounds by a combined method of mechanical grinding and pulse discharge sintering (MG-PDS), and measured their thermoelectric properties. Each of pure Mn and Si powders was mechanically ground using a planetary ball milling equipment at 400 rpm for 3 h. The ground powders with particle size of 44μm or less were individually collected by sieving. After mixing by using a rotary blender at 60 rpm for 1 h, HMS compound was synthesized from the powder mixture and simultaneously consolidated by PDS at 1173 K for 15 min under 60 MPa in a vacuum atmosphere. Si ratio in MnSix was changed from x = 1.73 to 1.9. Effect of the Si ratio on microstructure and thermoelectric properties was investigated. The maximum dimensionless figure of merit ZT= 0.83 was achieved at 818 K in MnSi1.84 sample.