Preparation And Thermoelectric Transport Properties Of In-doping β-Zn₄Sb₃ Bulk Thermoelectric Materials

has been considered as one of the most promising p-type thermoelectric materials in the moderate temperature range. How to optimize the thermoelectric properties ofβ-Zn4Sb3 compound is an urgent issue. In this thesis, a series of In-dopedβ-Zn4Sb3-based materials with nominal composition of Zn4Sb3-xInx (0～0.08,△x=0.02) were prepared by traditional processing. It is found that ZT values of these In-dopedβ-Zn4Sb3-based bulk materials remarkably enhanced and the highest ZT value reaches 1.13 for Zn4Sb2.94In0.06 at 700 K. In order to demonstrate the effect of In impurity on the thermoelectric properties of P-Zn4Sb3, three kinds of In-dopedβ-Zn4Sb3-based materials with nominal composition of Zn4Sb3-xInx(0～0.12,△x=0.03), Zn4-xInxSb3 (0～0.24,△x=0.03), and Zn4Sb3Inx (0～0.08,△x=0.02) were intentionally designed in manners of occupying Sb site, Zn site, and interstice sites with In, respectively. Three kinds of single-phase and crack free In-dopedβ-Zn4Sb3-based bulk materials had been synthesized by employing the optimized vacuum melting time and spark plasma sintering conditions. Emphasis was placed on the effect of In impurity on thermoelectric properties.For Zn4Sb3-xInx thermoelectric materials with In doping at Sb site, the low-temperature electrical conductivity remarkably increased, the intrinsic excitation at high temperature nearly disappeared, and the lattice thermal conductivity significantly depressed. ZTs of all In-doped Zn4Sb3-xInx thermoelectric materials were remarkably enhanced compared with undopedβ-Zn4Sb3 bulk material. Compared with the value of 0.88 of undopedβ-Zn4Sb3 bulk material, ZTs of Zn4Sb2.92In0.08 and Zn4Sb2.91In0.09 bulk materials reached to 1.37 and 1.29 at 700 K, increased by 56%and 47%, respectively..For Zn4-xInxSb3 thermoelectric materials with In doping at Zn site, the Seebeck coefficient enhanced and the lattice thermal conductivity decreased. ZTs of all In-doped Zn4-xInxSb3 thermoelectric materials were remarkably increased compared with undoped P-Zn4Sb3bulk material. Compared with the value of 0.84 of undoped bulk material, ZTs of Zn3.85In0.15Sb3 and Zn3.82In0.18Sb3 bulk materials reached to 1.28 and 1.41 at 700 K, increased by 52%and 68%, respectively.For Zn4Sb3Inx thermoelectric materials with In doping at interstice site, the electrical conductivity seem no change, while Seebeck coefficient enhanced and the lattice thermal conductivity depressed. ZTs of all In-doped Zn4Sb3Inx thermoelectric materials were enhanced. Compared with the value of 0.84 of undopedβ-Zn4Sb3 bulk material, the highest ZT value of Zn4Sb3In0.06 bulk material reaches 1.02 at 700 K, increased by 21%.