where tPD, tNP,tpep and tIF are the relaxation times correspondingto scattering from the point defect, nanoinclusions, phononephonon interactions and interfaces, respectively. Obviously, thereduction of kL in the composite samples should be attributed to theadditional phonon scattering from nanoinclusion (tNP) and theformed phase boundaries (tIF).Previous studies [39] have confirmed that all the interfaces,whether they are grain boundaries or phase boundaries or whetherthey belong to the coherent or incoherent interfaces, can inhibit theheat flow without exception through phonon scattering in thesystem, resulting in remarkable reduction in kL. Moreover, thestudies show that the thermal conductivity depends sensitively onthe interface density (interface area per unit volume) following auniversal curve. In other words, kL reduces gradually with theincreasing interface density. Undoubtedly, the volume fraction ofphase boundaries Fp (as listed in Table 1) increase with theincreasing GNs content for f(GNs)/BiSbTe composites. As shown inFig. 8(c), it is quite clear that kL for f(GNs)/BiSbTe decreases with theincreasing Fp, which is originated from the enhanced phononscattering by the incorporated nanosheets and the phase boundaries. Anomalously, k for the 0.3 vol.% GNs/BiSbTe compositesample is larger than that of the 0.4 vol.% GNs/BiSbTe sample, whichcan be attributed to its much higher kC caused by the increase inelectrical resistivity r
where tPD, tNP,tpep and tIF are the relaxation times corresponding<br>to scattering from the point defect, nanoinclusions, phononephonon interactions and interfaces, respectively. Obviously, the<br>reduction of kL in the composite samples should be attributed to the<br>additional phonon scattering from nanoinclusion (tNP) and the<br>formed phase boundaries (tIF).<br>Previous studies [39] have confirmed that all the interfaces,<br>whether they are grain boundaries or phase boundaries or whether<br>they belong to the coherent or incoherent interfaces, can inhibit the<br>heat flow without exception through phonon scattering in the<br>system, resulting in remarkable reduction in kL. Moreover, the<br>studies show that the thermal conductivity depends sensitively on<br>the interface density (interface area per unit volume) following a<br>universal curve. In other words, kL reduces gradually with the<br>increasing interface density. Undoubtedly, the volume fraction of<br>phase boundaries Fp (as listed in Table 1) increase with the<br>increasing GNs content for f(GNs)/BiSbTe composites. As shown in<br>Fig. 8(c), it is quite clear that kL for f(GNs)/BiSbTe decreases with the<br>increasing Fp, which is originated from the enhanced phonon<br>scattering by the incorporated nanosheets and the phase boundaries. Anomalously, k for the 0.3 vol.% GNs/BiSbTe composite<br>sample is larger than that of the 0.4 vol.% GNs/BiSbTe sample, which<br>can be attributed to its much higher kC caused by the increase in<br>electrical resistivity r
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