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SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements. However, the thermal stability is an important issue for commercial application. In particular, thermoelectric materials are in the high temperature for a long time due to the working condition. The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the internal of SnSe crystal is not easily oxidized, while the x-ray photoelectron spectroscopy (XPS) results indicate that the surface of SnSe is slight oxidized to SnO 2 . Even if the surface is oxidized, the SnSe crystal still exhibits stable thermoelectric properties. Meanwhile, the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air, which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe. Moreover, the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe. The density functional theory (DFT) calculation verifies the important role of defect on the electrical conductivity and electron configuration. In summary, appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.

In this study, a numerical approach to the fracture behavior in a three-unit zirconia-based fixed partial denture (FPD) framework was made under mechanical loading using a newly developed three-dimensional (3D) numerical modeling code. All the materials studied were treated heterogeneously and Weibull distribution law was applied to describe the heterogeneity. The Mohr-Coulomb failure criterion with tensile strength cut-off was utilized to judge whether the material was in an elastic or failed state. For validation, the fracture pattern obtained from the numerical modeling was compared with a laboratory test; they largely correlated with each other. Similar fracture initiation sites were detected both in the numerical simulation and in an earlier fractographic analysis. The numerical simulation applied in this study clearly described the stress distribution and fracture process of zirconia-based FPD frameworks, information that could not be gained from the laboratory tests alone. Thus, the newly developed 3D numerical modeling code seems to be an efficient tool for prediction of the fracture process in ceramic FPD frameworks.