The importance of phase equilibrium for doping efficiency: iodine doped PbTe

Male, James P.; Agne, Matthias T.; Goyal, Anuj; Anand, Shashwat; Witting, Ian T.; Stevanović, Vladan; Snyder, G. Jeffrey

doi:10.1039/c9mh00294d

Cited by 46 publications

(56 citation statements)

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“…Detailed experimental procedures can be found elsewhere. [ 21,30 ] As shown in Figure a, the Seebeck coefficient of the crystals show a transition from p‐type charge transport behavior to n‐type charge transport behavior after only 1 h Mg saturation annealing. After annealing, the absolute Seebeck coefficient increases with rising temperature, typical of degenerate semiconductors and is consistent with the results obtained previously in polycrystalline samples with similar electron concentrations.…”

Section: Figurementioning

confidence: 99%

“…In this study, we have successfully synthesized metallic n‐type Te‐doped Mg 3 Sb 2 single crystals using an Sb‐flux growth method followed by Mg saturation annealing. [ 21,30 ] These metallic n‐type single crystals enable us to investigate the intrinsic carrier transport mechanism. The electrical conductivity and carrier mobility exhibit a typical T −1.5 dependence, demonstrating that phonons dominate the scattering of charge carriers and no evidence of ionized impurity scattering is found.…”

Section: Figurementioning

confidence: 99%

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Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

et al. 2020

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Mg3(Sb,Bi)2 alloys have recently been discovered as a competitive alternative to the state‐of‐the‐art n‐type Bi2(Te,Se)3 thermoelectric alloys. Previous theoretical studies predict that single crystals Mg3(Sb,Bi)2 can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n‐type Mg3(Sb,Bi)2 single crystals. Here, the first thermoelectric properties of n‐type Te‐doped Mg3Sb2 single crystals, synthesized by a combination of Sb‐flux method and Mg‐vapor annealing, is reported. The electrical conductivity and carrier mobility of single crystals exhibit a metallic behavior with a typical T−1.5 dependence, indicating that phonon scattering dominates the charge carrier transport. The absence of any evidence of ionized impurity scattering in Te‐doped Mg3Sb2 single crystals proves that the thermally activated mobility previously observed in polycrystalline materials is caused by grain boundary resistance. Eliminating this grain boundary resistance in the single crystals results in a large enhancement of the weighted mobility and figure of merit zT by more than 100% near room temperature. This work experimentally demonstrates the accurate understanding of charge‐carrier scattering is crucial for developing high‐performance thermoelectric materials and indicates that single‐crystalline Mg3(Sb,Bi)2 solid solutions can exhibit higher zT compared to polycrystalline samples.

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

et al. 2020

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“…38 Similarly, Pb-excess in PbTe was found to suppress the formation of Pb-vacancies, leading to a full doping efficiency of I at the Te site. 39 Moreover, chemical potential was found to play an important role in controlling the native defects in Mg 2 Si. 40 However, in the case of a single band transport including n-PbTe, optimization of electronic performance requires a nearly constant reduced Fermi level, leading the optimal carrier concentration (n opt ) to be strongly temperature dependent via n opt $ (m d *T) 1.5 (m d * as the density-of-state effective mass), because of the temperature-induced broadening in Fermi distribution.…”

Section: The Bigger Picturementioning

confidence: 99%

Cu Interstitials Enable Carriers and Dislocations for Thermoelectric Enhancements in n-PbTe0.75Se0.25

Xiao

Nan

et al. 2020

Chem

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Aliovalent defects are extremely effective in manipulating charge transport and atomic vibrational properties for thermoelectric enhancements. Electronic performance of thermoelectrics is optimized at a reduced Fermi level of $0.3, which causes the optimal carrier concentration (n opt) to be strongly temperature dependent. This motivates a dynamic doping approach for electronic enhancements through an increase with temperature of solubility of aliovalent dopants. In addition, the defects could simultaneously act as scattering sources of phonons for reducing the lattice thermal conductivity. These effects are illustrated in this work by the temperature-dependent excess Cu solubility in n-PbTe 0.75 Se 0.25 thermoelectrics, in which both carriers and dislocations are induced for regulating the electronic and phononic transport properties for a realization of an extraordinary thermoelectric figure of merit. The resultant defect structures and temperature gradient doping effects (for aliovalent solutes) could in principle open extra possibilities for optimizing charge and phonon transport properties in thermoelectrics.

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“…[6,31] Although extrinsic doping offers an effective way of carrier optimization and zT enhancement, it inevitably brings concern on whether the band structure and mechanism of carrier scattering are affected. For example, the substitution of Pb by a cation, such as the Bi, [60] Ti, [61] I, [62] in n-type PbTe would lower the carrier mobility due to the deterioration of conduction band. In contrast, the intercalation of copper in n-type PbTe (Cu x PbTe 1−x ) [6] yields the best n-type performance, as a result of retaining the electronic band structure.…”

Section: (5 Of 11)mentioning

confidence: 99%

From Dislocation to Nano‐Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance in n‐Type PbTe

Deng

Wang

et al. 2020

Adv Funct Materials

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PbTe-based alloys have been widely used as mid-temperature thermoelectric (TE) materials since the 1960s. Years of endeavor spurred the tremendous advances in their TE performance. The breakthroughs for n-type PbTe have been somewhat less impressive, which limits the overall conversion efficiency of a PbTe-based TE device. In light of this obstacle, an n-type Ga-doped PbTe via an alternative thermodynamic route that relies on the equilibrium phase diagram and microstructural evolution is revisited. Herein, a plateau of zT = 1.2 is achieved in the best-performing Ga 0.02 Pb 0.98 Te in the temperature range of 550-673 K. Notably, an extremely high average zT ave = 1.01 is obtained within 300 − 673 K. The addition of gallium optimizes the carrier concentration and boosts the power factor PF = S 2 ρ −1. Meanwhile, the κ L of Ga-PbTe reveals a significantly decreasing tendency owing to the defect evolution that changes from dislocation loop to nano-precipitation with increasing Ga content. The pathway for both the κ L reduction and defect evolution can be probed by an equilibrium phase diagram, which opens up a new avenue for locating high zT TE materials.

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The importance of phase equilibrium for doping efficiency: iodine doped PbTe

Abstract: Drastic effects of phase equilibrium on semiconductor doping efficiency are demonstrated in n-type PbTe.

Cited by 46 publications

References 58 publications

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Cu Interstitials Enable Carriers and Dislocations for Thermoelectric Enhancements in n-PbTe0.75Se0.25

From Dislocation to Nano‐Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance in n‐Type PbTe

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The importance of phase equilibrium for doping efficiency: iodine doped PbTe

Abstract: Drastic effects of phase equilibrium on semiconductor doping efficiency are demonstrated in n-type PbTe.

Cited by 46 publications

References 58 publications

Metallic n‐Type Mg3Sb2 Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Metallic n‐Type Mg3Sb2 Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Cu Interstitials Enable Carriers and Dislocations for Thermoelectric Enhancements in n-PbTe0.75Se0.25

From Dislocation to Nano‐Precipitation: Evolution to Low Thermal Conductivity and High Thermoelectric Performance in n‐Type PbTe

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Resources

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Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance