Si_(100)P_(2.5)(GaP)_(1.5)中随机孔洞对热电性能的影响

Effects of random pores on the thermoelectric properties of Si_(100)P_(2.5)(GaP)_(1.5) bulk

纯硅由于原材料来源广、熔点高,是潜在的太阳能热发电用热电材料.它的热电绩效因子ZT很小,室温只有0.01.本研究小组通过掺杂和结构纳米化制备了Si_(100)P_(2.5)(GaP)_(1.5),获得813℃时的ZT为0.47.本文在此基础上,通过引入一种新的机制——随机孔洞——来进一步提高纯硅基材料Si_(100)P_(2.5)(GaP)_(1.5)的ZT.结果表明:由于孔洞增加了对低能载流子的过滤,Seebeck系数得到了提高;又由于孔洞对主要携带热量的声子的散射,晶格热导率大大降低,结果Si_(100)P_(2.5)(GaP)_(1.5)的ZT提高了32%.研究结果表明引入随机孔洞是增加纯硅基体系ZT的有效途径.

SiGe, as a reliable and most efficient high-temperature thermoelectrics, has been utilized in special fields for many years, but there is no large-scale commercial application due to its high cost and low efficiency. Therefore, it is necessary to improve the dimensionless figure of merit ZT of a Si-based system, free of Ge which is expensive and rare earth, thereby becoming competitive in cost and efficiency for the commercial application. Since pure silicon possesses rather low ZT, for example 0.01 at room temperature, we have developed doped and nano-structured Si100P2.5 （GaP）a.5 bulk material and obtained ZT 0.47. In this work, a new approach to inducing random pores with four size distributions of 50 nm, 100 nm, 300 nm, and 1-2 μm is applied to the SilooP2.5 （GaP）1.5 bulk material, and ZT is improved by 32%. The increase of ZT can be attributed to the enhancement of the electrical conductivity and the Seebeck coefficient, and the reduction of the lattice thermal conductivity. The enhancement of electrical conductivity is ascribed to the doping effect of a small amount of Sb, while the increase of Seebeck coefficients stems mainly from the filter of low-energy carriers, and the reduction of lattice thermal conductivity arises mainly from phonons scattering. It is proved in this work that inducing random pores is an effective approach to improving the figure of merit of Si-based system.