## 3 Results  
Figure 1a,b shows XRD patterns of the melt-spun ribbons of Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NiTe\({}_{2}\))\({}_{x}\) (\(x=0.1\)) and Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NbTe\({}_{2}\))\({}_{x}\) (\(x=0.1\)). Figure 1c,d shows XRD patterns of the SPS-sintered samples of Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NiTe\({}_{2}\))\({}_{x}\) (\(x=0,0.003,0.01,\) and 0.1) and Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NbTe\({}_{2}\))\({}_{x}\) (\(x=0,0.005,0.01,\) and 0.1). For all samples, the diffraction peaks of the major phase were related to the Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) structure (JCPDS #00-49-1713). The XRD patterns of Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NiTe\({}_{2}\))\({}_{0.1}\) and Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NbTe\({}_{2}\))\({}_{0.1}\) with x = 0.1 showed additional peaks of the segregated phases of NiTe\({}_{2}\) (JCPDS #01-089-2642) and NbTe\({}_{2}\) (JCPDS #00-021-0605), respectively. Thus, it was confirmed that in situ phase segregation is possible after applying a rapid solidification process. For the samples doped with small fractions (\(x\leq 0.01\)), no secondary phase was observed. However, it can be expected that the same phase segregation of NiTe\({}_{2}\), and NbTe\({}_{2}\) occurred while the amount of the segregations was too small to be detected by XRD. Figure 1e,f shows the lattice parameters calculated from the XRD patterns for Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NiTe\({}_{2}\))\({}_{x}\) (\(x=0,0.003,\) and 0.01) and Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\)(NbTe\({}_{2}\))\({}_{x}\) (\(x=0,0.005,\) and 0.01) with no changes in lattice parameters. Figure 2 represents a schematic of energy band diagrams at heterointerfaces formed between Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) and the secondary phases, based on the concept of carrier energy filtering [14; 15]. The main concept, which involves a Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) matrix with the precipitates, is illustrated in Figure 2. Carrier transfer induces band bending away from the heterointerfaces between the BiSbTe matrix and precipitates. The work function, electron affinity, and bandgap data for NiTe\({}_{2}\), NbTe\({}_{2}\), and Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) are shown in Table 1. The electron affinity of Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) is 4.50 eV and the band gap is 0.2 eV [15]. The work functions of NiTe\({}_{2}\) and NbTe\({}_{2}\) are 4.44 eV and 4.62 eV, respectively [17; 18]. Barrier potentials may form near the interface; the presence of the electrostatic potential causes energy-dependent scattering of carriers at the heterointerfaces for NiTe\({}_{2}\) and NbTe\({}_{2}\), with Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) forming potential barriers of approximately 0.26 and 0.08 eV, respectively, as depicted in Figure 2. When hole carriers pass near the surfaces of secondary phases, low energy carriers are scattered, inducing the carrier filtering effect [14; 15]. However, the energy blocking effect near the interfaces between NbTe\({}_{2}\) would be smaller due to their low barrier height of 0.08 eV (Figure 2b). Figure 3 shows the \(\sigma\) and \(S\) as a function of temperature of the samples after melt spinning with a small addition (\(x\leq 0.01\)). Bi\({}_{0.5}\)Sb\({}_{1.5}\)Te\({}_{3}\) exhibited an \(\sigma\) of 465 S/cm at room temperature. As shown in Figure 3a, no change in \(\sigma\) was observed for \(x=0.003\); however, the \(x=0.01\) showed an increased \(\sigma\) (\(\sim\)500 S/cm at room temperature). In Figure 3b, the \(S\) values, as a function of temperature, are shown, while there is no distinct change in the error range. However, as shown in inset of Figure 3b, the power factor (\(\sigma S^{2}\)) was increased from 2.68 to 3.15 mW/mK\({}^{2}\) for \(x=0.01\) as both the \(\sigma\) and \(S\) increased. In Figure 3c, after the addition of a small amount of NbTe\({}_{2}\), there is no significant change in the \(\sigma\). As in Figure 3d, the \(S\) shows no distinct change in error range by NbTe\({}_{2}\) addition.