Thermoelectric Properties of Ce/Pb Co-doped Polycrystalline In 4x Ce x Pb 0.01 Se 3 Compounds HENG ZHAN, 1 KUNLING PENG, 1,2 RASHED ALSHARAFI, 1 QIUFAN CHEN, 1 WEI YAO, 1 XU LU, 1 GUOYU WANG, 2 XIAONAN SUN, 1,3 and XIAOYUAN ZHOU 1,4 1.—College of Physics, Chongqing University, Chongqing 401331, People’s Republic of China. 2.—Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, People’s Republic of China. 3.—e-mail: xnsun168@cqu.edu.cn. 4.—e-mail: xiaoyuan2013@cqu.edu.cn In this study, the thermoelectric properties for polycrystalline In 4x Ce x Pb 0.01 Se 3 (x = 0.03, 0.06, 0.08, 0.1) compounds are investigated. Theoretical and experimental study reveal that the Ce/Pb co-doping at the In sites is an effective way to simultaneously decrease the thermal conductivity and in- crease the electric conductivity (Ahn et al. in Appl Phys Lett 99:102, 2011). As a heavy atom, Ce can effectively scatter phonons which reduces the thermal conductivity. Meanwhile, the Pb atom serving as electron donor provides additional electrons in the doped compounds. Therefore, the reduced thermal conductivity along with the boosted power factor give rise to an improvement of the dimensionless figure-of-merit, ZT, of over 65% in In 4x Ce x Pb 0.01 Se 3 (x = 0.06) compounds as compared with pure In 4 Se 3 . Key words: Heavy atom, In 4 Se 3 , low thermal conductivity, electron donor INTRODUCTION Nowadays, more and more countries are con- cerned with environment-friendly energy sources. Thermoelectric materials (TE) that directly convert waste heat or sunlight into electricity play an important role as promising new renewable energy. 2 The dimensionless figure-of-merit ZT = rS 2 /r, where r is the electrical conductivity, S is the Seebeck efficient, T is the absolute temper- ature, and r is the thermal conductivity including electronic thermal conductivity r e and lattice ther- mal conductivity r latt , is used to measure the efficiency of TE. 3,4 In general, two vital strategies including band engineering and structure engineer- ing 4 have been applied to achieve the reduction in lattice thermal conductivity and the enhancement in power factor (rS 2 ). Approaches of band engineer- ing include distortions in the density of states (DOS), the convergence of electronic bands, 5,6 and optimizing carrier concentrations. 4 Another strategy, namely structure engineering, includes introducing nanostructures, designing complex crystal structures, 7 and developing lower dimen- sional materials. 4 However, it remains an issue that S, r and r are strongly coupled with each other through carrier concentration. As such, more effort is required to tune these parameters independently for much higher ZT. Recently, the single crystal layered structure material, In 4 Se 3 , has been reported to exhibit a remarkable high ZT of 1.48 at 700 K. 8 Figure 1 shows the crystal structures of In 4 Se 3 , which consist of anionic layers of [In 3 Se 3 ]  and In atomic chains via Van der Waals force. 9 The low-dimensional layered structure has been found to have low thermal conductivity, 10 leading to good thermoelec- tric performance. However, there exist some issues impeding further improvement of In 4 Se 3 . For instance, the synthesis of reported single crystals In 4 Se 3 is time-consuming and the resultant prod- ucts are usually fragile. 11 In addition, anisotropic thermoelectric properties displayed in single crys- tals 12 make them unsuitable for practical applica- tion. Furthermore, the lattice thermal conductivity (Received June 6, 2016; accepted August 25, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-4920-8 Ó 2016 The Minerals, Metals & Materials Society