We report a high-yield synthesis of single-crystal hexagonal Sb2Te3 nanoplates using a solvothermal approach. The experimental results show that the concentration of capping agent CTAB played a key role in the formation of nanoplates. This new nanostructure may provide opportunity for the exploration of novel thermoelectric properties and have potential applications in thermoelectric nanodevices.

Thermoelectric power generation is one of the most promising techniques to use the huge amount of waste heat and solar energy. Traditionally, high thermoelectric figure-of-merit, ZT, has been the only parameter pursued for high conversion efficiency. Here, we emphasize that a high power factor (PF) is equivalently important for high power generation, in addition to high efficiency. A new n-type Mg 2 Sn-based material, Mg 2 Sn 0.75 Ge 0.25 , is a good example to meet the dual requirements in efficiency and output power. It was found that Mg 2 Sn 0.75 Ge 0.25 has an average ZT of 0.9 and PF of 52 μW·cm ·K−2 over the temperature range of 25-450°C, a peak ZT of 1.4 at 450°C, and peak PF of 55 μW·cm·K −2 at 350°C. By using the energy balance of one-dimensional heat flow equation, leg efficiency and output power were calculated with T h = 400°C and T c = 50°C to be of 10.5% and 6.6 W·cm −2 under a temperature gradient of, respectively.thermoelectrics | magnesium | tin | power factor | output power T hermoelectric power generation from waste heat is attracting more and more attention. Potential fuel efficiency enhancement by recovering the waste heat is beneficial for automobiles and many other applications (1, 2). In addition, solar thermoelectric generator provides an alternative route to convert solar energy into electrical power besides the photovoltaic conversion (3). Thermoelectric generator (TEG) can be regarded as a heat engine using electrons/holes as the energy carrier. The conversion efficiency of a TEG is related to the Carnot efficiency and the material's average thermoelectric figure of merit ZT (4):where ZT = (S 2 σ/κ)T, and S, σ, κ, and T are Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. Pursuing high ZT has been the focus of the entire thermoelectric community by applying various phonon engineering via nanostructuring approaches to reduce the thermal conductivity (5-7), or by exploring new compounds with intrinsically low thermal conductivity, such as compounds having complex crystalline structure, local rattlers, liquid-like sublattice, and highly distorted lattice (8-11). However, for practical applications, efficiency is not the only concern, and high output power density is as important as efficiency when the capacity of the heat source is huge (such as solar heat), or the cost of the heat source is not a big factor (such as waste heat from automobiles, steel industry, etc.). The output power density ω is defined as the output power W divided by the cross-sectional area A of the leg, i.e., ω = W/A, which is related to power factor PF = S 2 σ by the following:Eq. 2 contains two main parts: square of the temperature difference divided by leg length, and material power factor PF = S 2 σ.Clearly, to achieve higher power density for a given heat source, we have to either increase the power factor PF or decrease the leg length. However, decreasing the leg length could cause severe consequences such as increase of large heat flux that will incr...

Neutron diffraction measurements are presented exploring the magnetic and structural phase behaviors of the candidate J ef f = 1/2 Mott insulating iridate Sr2IrO4. Comparisons are drawn between the correlated magnetism in this single layer system and its bilayer analog Sr3Ir2O7 where both materials exhibit magnetic domains originating from crystallographic twinning and comparable moment sizes. Weakly temperature dependent superlattice peaks violating the reported tetragonal space group of Sr2IrO4 are observed supporting the notion of a lower structural symmetry arising from a high temperature lattice distortion, and we use this to argue that moments orient along a unique in-plane axis demonstrating an orthorhombic symmetry in the resulting spin structure. Our results demonstrate that the correlated spin order and structural phase behaviors in both single and bilayer Srn+1IrnO3n+1 systems are remarkably similar and suggest comparable correlation strengths in each system.

The copper silver selenide has two phases: the low-temperature semimetal phase (α-CuAgSe) and high-temperature phonon-glass superionic phase (β-CuAgSe). In this work, the electric transport and thermoelectric properties of the two phases are investigated. It is revealed that the β-CuAgSe is a p-type semiconductor and exhibits low thermal conductivity while the α-CuAgSe shows metallic conduction with dominant n-type carriers and low electrical resistivity. The thermoelectric figure of merit zT of the polycrystalline β-CuAgSe at 623 K is ~0.95, suggesting that superionic CuAgSe can be a promising thermoelectric candidate in the intermediate temperature range.

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