Synthesis and characterization of metal silicides including volatile metals

通过对组成元素进行加热，合成了新型三元钠镁锡铅化物Na2MgX （X=Sn, Pb）、Na2Mg3X2、（X=Sn, Pb）和Na4Mg4Sn3。通过单晶x射线衍射测定了它们的晶体结构，并通过测量的塞贝克系数和电导率估算了热电功率因子。Na2MgSn以li2cuas型结构(六边形，P63/mmc, Z = 2, a = 0.50486（11) nm, c = 1.0095(2) nm）结晶，在300 K时功率因数最高，为1.5 × 10-3 Wm-1K-1。以Mg2Si粉为原料，在873 K温度下，500 Pa压力下加热40 h，制备了微孔多晶Si粉。多孔硅颗粒由亚微米到微米大小的硅晶体和开放空间组成。多孔Si晶粒的形成是由于Mg2Si晶粒中Mg的蒸发，然后Si的结晶。

New ternary sodium-magnesium stannides and plumbides, Na2MgX (X=Sn, Pb), Na2Mg3X2, (X=Sn, Pb), and Na4Mg4Sn3, were synthesized by heating the constituent elements. Their crystal structures were determined by single-crystal X-ray diffraction and the thermoelectric power factors were estimated from the measured Seebeck coefficients and electrical conductivities. Na2MgSn, which crystallizes in the Li2CuAs-type structure (hexagonal, P63/mmc, Z = 2, a = 0.50486(11) nm, c = 1.0095(2) nm), showed highest power factor of 1.5x10-3 Wm-1K-1 at 300 K among the novel compounds.Polycrystalline Si powder consisting of micro-porous grains was prepared by heating Mg2Si powder at 873 K for 40 h under a pressure of 500 Pa. The porous Si grains were composed of submicrometer- to micrometer-sized Si crystals with open spaces. The formation of the porous Si grains was attributed to Mg evaporation from Mg2Si grains, followed by crystallization of Si.