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As a most promising mid‐temperature thermoelectric material, CoSb3‐based bulk material exhibits an applicable figure‐of‐merit (ZT) of more than one. However, their fabrication is historically time‐consuming due to the long‐time solid‐state phase transitions from CoSb2 to CoSb3. To overcome this challenge, here, a fast one‐step process is developed to fabricate n‐type Yb‐doped CoSb3 with stable ZT of 1.12 at 765 K in <5 h. Experiments confirm Yb promotes peritectic reactions of CoSb + Liquid → CoSb2 and CoSb2 + Liquid → CoSb3, optimizes power factor, and suppresses thermal conductivity. Moreover, the dense grains, induced by the one‐step crystallization, result in outstanding mechanical properties with a Young's modulus of 171.4 GPa and a hardness of 8.8 GPa in the Yb‐doped CoSb3. This study indicates that the fast one‐step fabrication route can effectively promote the practical applications of CoSb3‐based thermoelectrics and provide guidance for thermoelectric fabrication via rational phase design. [ABSTRACT FROM AUTHOR]

Realizing high thermoelectric performance in CoSb3 skutterudite‐based thin films and their devices is historically challenging, especially due to the lack of high‐performing thin‐film‐based device working at medium‐to‐high temperatures. Here, a record‐high ZT of 1.1 is achieved at 683 K in an n‐type Ce0.3Ni1.5Co2.5Sb12 thin film, fabricated from a self‐designed target via advanced pulsed laser deposition. Both experimental and computational results confirm that the Ce‐filling and metal‐featured nanoinclusions such as CeSb contribute to high electrical conductivity, while the Ni‐doping and significantly strengthen the energy filtering effect that occurs at the dense interfaces between the Ce0.3Ni1.5Co2.5Sb12 matrix and the nanoinclusions which leads to a large Seebeck coefficient, giving rise to such a high ZT. In addition, a new‐type CoSb3 thin‐film‐based device is successfully fabricated, which exhibits a high output power density of 8.25 mW cm−2 at a temperature difference of 140 K and a cold‐side temperature of 573 K, indicating the potential for application to medium‐to‐high‐temperature power generation scenarios. [ABSTRACT FROM AUTHOR]

In this work, silica‐based ceramic cores with alumina as a mineralizer were prepared via an injection molding method, and the effects of alumina on the microstructural evolution and properties at 1450°C (simulating the process of equiaxed castings) and 1550°C (simulating the process of columnar/single crystal castings) were investigated. It was found that alumina promoted the cristobalite crystallization of fused silica refractory during sintering but inhibited the devitrification rate in the subsequent heating. The flexural strength of silica‐based ceramic cores at an ambient temperature and 1450°C improved with an increasing alumina content, whereas the opposite trend appeared at 1550°C. The creep resistances of silica‐based cores were improved significantly and then slightly deteriorated with an increasing alumina content from 5% to 20%, depending on the competition effects of alumina hindering the viscous flow of liquid silica (favorable), but suppressing the devitrification rate (unfavorable). The results of this work show that silica‐based cores need to follow different compositional design principles for equiaxed and columnar/single‐crystal turbine blade castings. [ABSTRACT FROM AUTHOR]

Al-4.5wt.%Cu alloy has been directionally solidified at constant and abruptly changing withdrawal rates, respectively. The effects of the withdrawal rate on solidification microstructure, primary dendrite arm spacing (PDAS) and liquid solute distribution in front of the solid-liquid interface were investigated. The experimental results for the PDAS at a constant withdrawal rate agree well with the values calculated by the Hunt, Trivedi and Hunt-Lu models. At an abrupt change in the withdrawal rate, the maximum to minimum ratio of the PDAS at a given solidification parameter, i.e. λ1max/λ1min, is more than 2, and the PDAS values are remarkably history-dependent. Further, the liquid-solute distribution curve based on theoretical calculation shows that the larger the initial withdrawal rate is, the smaller the minimum of liquid solute concentration in front of the solid-liquid interface is after the abrupt change in withdrawal rate.

The directionally solidifi ed microstructure of Sn-16%Sb hyperperitectic alloy has been investigated at various solidifi cation rates using a high-thermal gradient directional solidifi cation apparatus. The results indicate that the solidifi cation microstructure consists of hard primary intermetallic SnSb phase embedded in a matrix of soft peritectic β-Sn phase. The primary SnSb phase exhibits faceted growth with tetragonal or trigonal shapes. At the same time, the primary SnSb phase is refi ned with an increase in the solidifi cation rate and dispersed more uniformly in the matrix of β-Sn phase. The volume fraction of the SnSb phase fi rstly decreases and then increases when the solidifi cation rate increases in directional solidifi cation of Sn-16%Sb hyperperitectic alloy.