The reaction of MnTe with AgSbTe 2 in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe 3 . AgMnSbTe 3 crystallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe 3 is a p-type semiconductor with a narrow optical band gap of ∼0.36 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag 2 Te nanograins precipitate at grain boundaries of AgMnSbTe 3 . The energy offset of the valence band edge between AgMnSbTe 3 and Ag 2 Te is ∼0.05 eV, which implies that Ag 2 Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ∼12.2 μW cm −1 K −2 at 823 K, ultralow lattice thermal conductivity of ∼0.34 W m −1 K −1 (823 K), high peak ZT of ∼1.46 at 823 K, and high average ZT of ∼0.87 in the temperature range of 400−823 K.

A new p-type high entropy semiconductor AgMnGeSbTe 4 with a band gap of ≈0.28 eV is reported as a promising thermoelectric material. AgMnGeSbTe 4 crystallizes in the rock-salt NaCl structure with cations Ag, Mn, Ge, and Sb randomly disordered over the Na site. Thus, a strong lattice distortion forms from the large difference in the atomic radii of Ag, Mn, Ge, and Sb, resulting in a low lattice thermal conductivity of 0.54 W m −1 K −1 at 600 K. In addition, the AgMnGeSbTe 4 exhibits a degenerate semiconductor behavior and a large average power factor of 10.36 µW cm −1 K −2 in the temperature range of 400-773 K. As a consequence, the AgMnGeSbTe 4 has a peak figure of merit (ZT) of 1.05 at 773 K and a desirable average ZT value of 0.84 in the temperature range of 400-773 K. Moreover, the thermoelectric performance of AgMnGeSbTe 4 can be further enhanced by precipitating of Ag 8 GeTe 6 , which acts as extra scatting centers for holes with low energy and phonons with medium wavelength. The simultaneous optimization in power factor and lattice thermal conductivity yields a peak ZT of 1.27 at 773 K and an average ZT of 0.92 (400-773 K) in AgMnGeSbTe 4 -1 mol% Ag 8 GeTe 6 .

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Purpose Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit cell topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods. Design/methodology/approach The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit cell topology on the compression properties of SLM-processed porous scaffolds. Findings The Mises stress predicted by FE simulations showed that different unit cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro cell culture experiment. Originality/value A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit cell topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants.

Both hexagonal and cubic Mg x Zn 1−x O (0 x 0.6) films were grown on c-plane (0001) sapphire substrate at low temperature. X-ray diffraction measurements show that the cubic Mg x Zn 1−x O films grow along the [111] direction while the hexagonal ZnO films grow along [0001]. The temperaturedependent optical properties of Mg x Zn 1−x O films were measured by ultraviolet optical transmission with temperature variation from 10 to 300 K and analysed by theoretically fitting the optical absorption spectra. For Mg x Zn 1−x O with 0 < x 0.51, only stable hexagonal phase was observed and the optical absorption edge red shifts with temperature increase monotonically. For Mg x Zn 1−x O with x 0.55, the crystal structure is cubic at 300 K. However, as measurement temperature decreases from 300 to 10 K an abnormality of the optical absorption is observed, which is attributed to the possible phase transition from cubic to hexagonal structure. The underlying physical mechanism for the crystal phase transition is attributed to the interaction of stress with stacking faults in the cubic Mg x Zn 1−x O.