Yb/Sr双原子复合填充的Ⅰ-型Yb_x Sr_(8-x)Ga_(16)Ge_(30)笼合物的合成及热电性能

用熔融法结合放电等离子烧结(SPS)合成了Yb/Sr双原子复合填充的n型Yb_x Sr_(8-x)Ga_(16)Ge_(30)(x=0,0.5,1.0,1.5)笼合物,研究了双原子复合填充及Yb填充量x对Yb_x Sr_(8-x)Ga_(16)Ge_(30)笼合物热电传输特性的影响规律.结果表明,Yb在Yb_x Sr_(8-x)Ga_(16)Ge_(30)化合物中的固溶极限介于1.0-1.5之间.随着Yb填充量x的增加,化合物的室温载流子浓度增加而迁移率降低.在300-800 K温度范围内,随着x的增加,双原子填充试样的电导率逐渐增大,Seebeck系数逐渐减小,其中x=0.5的试样与单原子填充的Sr_8Ga_(16)Ge_(30)试样相比,电导率变化不大,Seebeck系数显著增加.Yb/Sr双原子复合填充比Sr单原子填充更有利于晶格热导率的降低,且晶格热导率随着Yb填充量x的增加逐渐降低.在所有n型Yb_x Sr_(8-x)Ga_(16)Ge_(30)化合物中Yb_(1.0) Sr_(7.0)Ga_(16)Ge_(30)化合物的ZT值最大,在800 K时其最大ZT值达0.81,与单原子填充的Sr_8Ga_(16)Ge_(30)化合物相比ZT值提高了35%.

Abstract：

n-type Yb/Sr double-atom-filled Yb_xSr_(8-x)Ga_(16)Ge_(30) (x = 0, 0.5, 1.0, 1.5) elathrates have been synthesized by combining melting reaction with the spark plasma sintering (SPS) method. The effects of double-atom fining on thermoelectric properties have been investigated. The results show that the solubility limit of Yb in the Sr-Ga-Ge system is between 1.0 and 1.5 when it is expressed by the formula of Yb_xSr_(8-x)Ga_(16)Ge_(30). With increasing Yb content x, the room-temperature carrier concentration of the Yb_xSr_(8-x)Ga_(16)Ge_(30) samples increases, while the room-temperature carrier mobility decreases. For the double-atom-filled samples, the electrical conductivity raises with increasing x, while the Seebeck coefficient reduces, and in which the x = 0.5 sample has a comparable electrical conductivity and a remarkably higher $eebeck coefficient compared with the single-atom-filled Sr_8Ga_(16)Ge_(30) sample in the temperature range of 300-800 K. The double-atom filling of Yb/Sr has significant influence on the lattice thermal conductivity of the Yb_xSr_(8-x)Ga_(16)Ge_(30) samples and the lattice thermal conductivity decreases gradually with increasing x. Of all the Yb_xSr_(8-x)Ga_(16)Ge_(30) samples, the maximum dimensionless figure of merit ZT of 0.81 is obtained at 800 K for the Yb_(1.0)Sr_(7.0)Ga_(16)Ge_(30) sample. Compared with that of single-atom-filled Sr_(8-x)Ga_(16)Ge_(30) sample, it is 35% higher at the same temperature.