Enhanced thermoelectric performance in the very low thermal conductivity Ag2Se0.5Te0.5

Drymiotis, Fivos; Day, Tristan; Brown, David R.; Heinz, Nicholas A.; Snyder, G. Jeffrey

doi:10.1063/1.4824353

Cited by 49 publications

(51 citation statements)

References 24 publications

(24 reference statements)

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“…[2][3][4][5][6][7][8] Further study reveals that the zT is significantly enhanced at 400 K during the phase transition in Cu 2 Se and the improved cooling ability is confirmed by the test of the module using the Cu 2 Se and Yb-filled skutterudite. 9,10 The abnormal electrical and thermal transport in Cu 2 Se draws the interests to other Cu-and Ag-based compounds having similar chemical formulas.…”

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confidence: 64%

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Qiu

Zhang

et al. 2014

Applied Physics Letters

145

157

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Small amount of Se atoms are used to tune the carrier concentrations (nH) and electrical transport in Ag2Se. Significant enhancements in power factor and thermoelectric figure of merit (zT) are observed in the compositions of Ag2Se1.06 and Ag2Se1.08. The excessive Se atoms do not change the intrinsically electron-conducting character in Ag2Se. The detailed analysis reveals the experiment optimum carrier concentration in Ag2Se is around 5 × 1018 cm−3. We also investigate the temperature of maximum zT and the thermoelectric transport during the first order phase transitions using the recently developed measurement system.

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confidence: 64%

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Qiu

Zhang

et al. 2014

Applied Physics Letters

145

157

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“…5,6 This superionic state results in extremely low lattice thermal conductivity values as low as 0.4 W(Km) -1 in the superionic phase and in turn a high figure of merit. Starting with the superionic Cu2-δSe, many other superionic copper and silver selenides have been found to be interesting thermoelectrics; for instance the argyrodites Cu7PSe6, 7 Ag2Se, [8][9][10] CuAgSe, 11,12 and quaternary copper chalcogenides Cu2MM'Q4 (M=Zn, Fe,..; M' = Zn, Ge, Q = S, Se, Te) which also exhibit interstitial copper ions and even show band convergence. [13][14][15] While copper selenide has potential as a thermoelectric material at high temperatures, its ionic conductivity has caused long-term stability problems for use in thermoelectric generators.…”

Section: Introductionmentioning

confidence: 99%

Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu_2-ySe_1–xBr_x

et al. 2015

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X-ray diffraction data modeling. Powder diffraction patterns were modeled using a small, anorthic unit cell derived from a LP search (TOPAS Academic V4.1). Figure S1 shows the x-ray powder diffraction data of the synthesized Cu2-δSe with the corresponding Pawley fit. A triclinic unit cell with a = 7.082(8) Å, b = 4.121(3) Å, c = 7.121(3) Å, α = 106.1(0), β = 99.1(0)° and γ = 90.1(4)° has been utilized for the fits in order to determine lattice parameters for each composition.

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“…Here, a schematic phase diagram having a miscibility gap is used for demonstration ( Figure a). In general, however, many thermoelectric alloys and composites have been made in systems having more complicated phase diagrams …”

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Phase Transformation Contributions to Heat Capacity and Impact on Thermal Diffusivity, Thermal Conductivity, and Thermoelectric Performance

2019

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Although direct measurements of κ are possible, [2] it is more frequent in measurement above room temperature to calculate thermal conductivity through the relation (Note S1, Supporting Information)Here, D [m 2 s −1 ] is the thermal diffusivity and ρc p = (∂H/∂T) p is the constant pressure heat capacity [J m −3 K −1 ] typically calculated from experimental bulk density, ρ [kg m −3 ] and the mass specific heat c p [J kg −1 K −1 ]. Equation (1) is utilized largely because measurements of thermal diffusivity, D, are accurate (within ≈3%) and easily accessible. [2] Thus, the uncertainty in calculating κ (often 10% or more) is frequently attributed to measurement of heat capacity. [2,3] Due to the uncertainty in the absolute magnitude of high temperature heat capacity measurements, it is often more accurate to use a model. Usually, the temperature independent Dulong-Petit heat capacity is a good approximation (within ≈5%) near room temperature. At higher temperatures, a model that incorporates a linear temperature dependence may be appropriate. [2,4,5] However, an incomplete understanding of heat capacity measurements and models can lead to inaccurate estimations of κ in some systems, especially those having substantial latent heats (e.g., during phase transitions). The recent debate surrounding the thermoelectric material, Cu 2 Se, is an excellent example. [6][7][8][9][10][11] In this material, and others, [12][13][14] the thermal diffusivity drops markedly as the material undergoes a phase transition. Depending on the heat capacity used to calculate κ, a maximum zT between 0.6 [7] and 2.3 [6] has been reported due to the superionic phase transition in Cu 2 Se. As exemplified in Figure 1, the choice of heat capacity can have a drastic impact on zT values.To properly characterize the behavior of thermal conductivity through a phase transition, it is paramount to understand the concurrent behavior of heat capacity. Recognizing that the total capacity of a material to absorb heat includes both the intrinsic heat capacity of the phases present and the enthalpy (heat) of transformation ΔH that is required to maintain equilibrium (characterized by the order parameter φ) as the temperature is changedThe accurate characterization of thermal conductivity κ, particularly at high temperature, is of paramount importance to many materials, thermoelectrics in particular. The ease and access of thermal diffusivity D measurements allows for the calculation of κ when the volumetric heat capacity, ρc p , of the material is known. However, in the relation κ = ρc p D, there is some confusion as to what value of c p should be used in materials undergoing phase transformations. Herein, it is demonstrated that the Dulong-Petit estimate of c p at high temperature is not appropriate for materials having phase transformations with kinetic timescales relevant to thermal transport. In these materials, there is an additional capacity to store heat in the material through the enthalpy of transformation ΔH. This can be described using a generalize...

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Enhanced thermoelectric performance in the very low thermal conductivity Ag2Se0.5Te0.5

Cited by 49 publications

References 24 publications

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu_2-ySe_1–xBr_x

Phase Transformation Contributions to Heat Capacity and Impact on Thermal Diffusivity, Thermal Conductivity, and Thermoelectric Performance

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Enhanced thermoelectric performance in the very low thermal conductivity Ag2Se0.5Te0.5

Cited by 49 publications

References 24 publications

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu2-ySe1–xBrx

Phase Transformation Contributions to Heat Capacity and Impact on Thermal Diffusivity, Thermal Conductivity, and Thermoelectric Performance

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Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu_2-ySe_1–xBr_x