Thermoelectric Properties And Signle Crystal Growth Of Bi₂Se₃ With Topology Insulator Dopant

is a promising topology insulation a material has attracted substantial interest in recently years. A series of Bi2Se3 based materials with nominal composition Bi2Se3+x (x=0,0.06,0.12,0.18,0.24) and Bi2-xYbxSe3 (x=0,0.02,0.04, 0.06,0.08,0.10) have been prepared by a melting-quenching-annealing-spark plasma sintering method. The effects of excessive Se and Yb doping of Bi site on the phase composition, microstructure and thermoelectric transport properties of these material were investigate and the process conditions of single crystal growth for the Yb-doped Bi2Se3 with nominal composition Bi2-xYbxSe3 (0～0.04,Δx=0.02) were explored in the paper.The bulk materials with nominal composition Bi2Se3+x (x=0,0.06,0.12,0.18, 0.24) were composed by single Bi2Se3 phase. Hall and Seebeck coefficients of all samples are negative exhibiting p-type conductivity and majority of carriers are electrons. With the increasing of the amount of excessive Se x, electrical conductivity and absolute value of Seebeck coefficient decreased, the variation on thermal conductivity is very slight. As a result, the ZT values of all sample decreased monotonously. The highest ZT value of 0.58 and lowest ZT values of 0.29 were obtained for the sample with x=0 at 425 K and x=0.24 at 320 K, respectively. The results indicated that adjusting excessive Se x was not a effective way to lower the carrier concentration and achieve topology insulator transformation.The bulk materials with nominal composition Bi2-xYbxSe3 (x=0,0.02,0.04,0.06, 0.08,0.10) were composed by the single-phase Bi2Se3. With increasing the Yb content x, the electrical conductivity decreased, the absolute value of Seebeck coefficient overall decreased, thermal conductivity increasing remarkably, ZT value was decreased. The ZT value of x=0.08 and 0.10 samples are very close to 0 at 320K, respectively reaches 0.0005 and 0.004. At the temperature below 350K, Bi1.9oYb0.10Se3 occurs a n-type to p-type transformation, it means Yb doped Bi2Se3 materials can be used as the topology insulator-based materials for single crystal growth.For the first time, Yb-doped centimeter-level Bi2Se3 single crystals with nominal compositions of Bi2-xYbxSe3 (x=0,0.02,0.04) was growen by vertical Bridgman method. The effect of the furnace temperature field, growth location, crucible lowering rate, crucible spin rate, and furnace atmosphere to the crystal quality was investigated. The initial optimized conditions were:nitrogen atmosphere, the program temperature 640℃, crucible lowering rate at 2 mm/h, crucible spin rate at 5.0 r/min.