Sr_3YCo_(4-x)Mg_xO_(10.5+δ)(0≤x≤0.04)多晶的制备和热电输运性质研究

Preparation and Thermoelectric Transport Properties of Sr_3YCo_(4-x)Mg_xO_(10.5+δ)( 0≤x≤0. 04) Polycrystalline

采用固相反应法制备Sr_3YCo_(4-x)Mg_xO_(10.5+δ)(0≤x≤0.04)系列多晶,研究了Mg掺杂对体系结构、电输运和热电性质的影响。结果表明系列多晶为四方晶系,由于掺入的Mg^(2+)(0.066 nm)部分替代了Co^(3+/4+)(0.053 nm/0.061nm),使晶格膨胀;多晶热电势在340~830 K随温度升高而下降,且Mg掺杂对热电势影响不大,表明Mg掺杂对体系载流子浓度影响不大;多晶电阻率在100~300 K随温度升高而降低,且随着掺杂量增加电阻率降低,结合扫描电镜观察到多晶的气孔数目减少、晶粒连接紧密和热电势的结果认为Mg掺杂对体系电输运性质的影响机制主要是使气孔、晶界散射作用减弱、载流子迁移率变大,而Mg掺杂对载流子浓度的影响是次要的。

Sr3YCo4-xMgxO10.5＋δ（0≤x≤0.04） polycrystalline samples were prepared by solid state reaction method. The Mg doping effects on the crystal structure, electrical transport property and thermopower were studied. The results of crystal structure indicate that Sr3YCo4-xMgxO10.5＋δ is tetragonal structure. Due to Mg2＋ （0. 066 nm） partly substitude Co3＋/4＋ （0. 053 nm/0. 061 nm）, and the Mg doping enlarge the lattice＂ parameters. The Seebeck coefficient measurement at 340 - 830 K shows that the thermopower decreases with increasing temperature, and Mg doping does not much affect the thermopower and carrier concentration. The resistivity measurement at 100 - 300 K shows that the resistivity decreases with increasing temperature and resistivity decreases with increasing Mg content. Scanning electron microscope results show that the number of pores decreases and grains connect closely. Combining the results of scanning electron microscope and thermopower indicate that the main effects of Mg doping impact on the electrical transport property are weaken the scattering of pores and grain boundaries, and improve the cartier mobility. The effects of carrier concentration is secondary.