The Atomic Circus: Small Electron Beams Spotlight Advanced Materials Down to the Atomic Scale

Wu, Haijun; Zhao, Xiuxi; Guan, Cao; Zhao, Li‐Dong; Wu, Jiagang; Song, Dongsheng; Li, Changjian; Wang, John; Loh, Kian Ping; Venkatesan, T.; Pennycook, Stephen J.

doi:10.1002/adma.201802402

Cited by 29 publications

(17 citation statements)

References 121 publications

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“…Making appropriate beneficial crystal defects allows one to obtain superior properties over those predicted by “perfect” structures. This has been a strategy of turning imperfections into benefit 1 , 2 . With precision structural controls at varying levels: micro, meso, nano, and even down to the atomic-scale structural defects, grains, precipitates, interfaces, stacking faults, and dislocations have been widely employed to optimize materials properties.…”

Section: Introductionmentioning

confidence: 99%

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Ning

Waqar

et al. 2021

Nat Commun

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Traditional strategies for improving piezoelectric properties have focused on phase boundary engineering through complex chemical alloying and phase control. Although they have been successfully employed in bulk materials, they have not been effective in thin films due to the severe deterioration in epitaxy, which is critical to film properties. Contending with the opposing effects of alloying and epitaxy in thin films has been a long-standing issue. Herein we demonstrate a new strategy in alkali niobate epitaxial films, utilizing alkali vacancies without alloying to form nanopillars enclosed with out-of-phase boundaries that can give rise to a giant electromechanical response. Both atomically resolved polarization mapping and phase field simulations show that the boundaries are strained and charged, manifesting as head-head and tail-tail polarization bound charges. Such charged boundaries produce a giant local depolarization field, which facilitates a steady polarization rotation between the matrix and nanopillars. The local elastic strain and charge manipulation at out-of-phase boundaries, demonstrated here, can be used as an effective pathway to obtain large electromechanical response with good temperature stability in similar perovskite oxides.

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Section: Introductionmentioning

confidence: 99%

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Ning

Waqar

et al. 2021

Nat Commun

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“…[22,46,56] In order to directly observe the interstitials, STEM ABF with stronger strain contrast was employed together with the STEM HAADF imaging mode. [57][58]…”

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confidence: 99%

Amphoteric Indium Enables Carrier Engineering to Enhance the Power Factor and Thermoelectric Performance in n‐Type Ag_nPb₁₀₀In_nTe₁₀₀₊₂_n (LIST)

Xiao

Wang

et al. 2019

Advanced Energy Materials

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The Ag and In co-doped PbTe, Ag n Pb 100 In n Te 100+2n (LIST), exhibits n-type behavior and features unique inherent electronic levels that induce self-tuning carrier density. Results show that In is amphoteric in the LIST with forming both In 3+ and In 1+ centers. Through unique interplay of valence fluctuations in the In centers and conduction band filling, the electron carrier density can be increased from ~ 3.1×10 18 cm -3 at 323 K to ~ 2.4×10 19 cm -3 at 820 K, leading to large power factors peaking at ~16.0 µWcm -1 K -2 at 873 K. The lone pair of electrons from In + can be thermally continuously promoted into the conduction band forming In 3+ , consistent with the amphoteric character of In. Moreover, with rising temperature, the Fermi level shifts into the conduction band, which enlarges the optical band gap based on the Moss-Burstein effect, and reduces bipolar diffusion and thermal conductivity. Adding extra Ag in LIST improves the electrical transport properties and meanwhile lowers the lattice thermal conductivity to ~ 0.40 Wm -1 K -1 . The addition of Ag creates spindle-shaped Ag 2 Te nanoprecipitates and atomic-scale interstitials which scatter a broader set of phonons. As a result, a maximum ZT value ~ 1.5 at 873 K was achieved in Ag 1.05 Pb 100 InTe 102 (LIST).

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“…These nanostructures are almost invisible in the STEM HAADF imaging mode, while quite clear in the STEM ABF imaging mode. STEM HAADF produces contrast interpretable by Z contrast thus sensitive to composition variation, while STEM ABF has weaker Z‐dependence, but sensitive to strain field . The STEM‐EDS (energy‐dispersive X‐ray spectroscopy) mappings in Figure S8, Supporting Information, reveals a homogeneous elemental distribution, even the nanostructures are observed in STEM images.…”

Section: Resultsmentioning

confidence: 99%

“…This reduction can be attributed to the strongly strengthened phonon scattering by point defects from PbSe alloying, [46] which can be further demonstrated by the Callaway model. [52,53] The STEM-EDS (energy-dispersive X-ray spectroscopy) mappings in Figure S8, Supporting Information, reveals a homogeneous elemental distribution, even the nanostructures are observed in STEM images. For (PbSe) 1−x (PbS) x alloys as shown in Figure S9, Supporting Information, the room-temperature κ lat well fits the Callaway-model in the whole alloying range.…”

Section: Resultsmentioning

confidence: 99%

Comprehensive Investigation on the Thermoelectric Properties of p‐Type PbTe‐PbSe‐PbS Alloys

Qin

Zhang

et al. 2019

Adv Elect Materials

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these parameters complicates the efforts in enhancing the thermoelectric performance. [1,3] To date, high ZT values have been obtained through enhancing electrical transport properties, reducing lattice thermal conductivities, and exploring the thermoelectric materials with intrinsically low thermal conductivity. [7][8][9][10][11][12][13][14][15][16][17][18][19] Lead chalcogenides are kinds of superior thermoelectrics because of their special physical and chemical properties. [20] In particular, PbTe and PbSe possess complex band structures (such as small energy offsets between light L and heavy Σ hole valence bands), which lead to larger band effective mass, higher Seebeck coefficients, and favor better electrical performance than that with single valence band. [9,[20][21][22] Besides, the intrinsic lattice thermal conductivities of lead chalcogenides are quite low due to the phonon anharmonicity. [20] Even that PbS possesses simple band structures and poor electrical and thermal transport properties, the features of low-cost, earth-abundant, higher melting point (1391 K), and larger energy band gap (0.41 eV) make PbS also an attractive thermoelectric candidate. [23][24][25] In the past few years, several approaches have been employed to enhance the thermoelectric performance of lead chalcogenides, such as enhancing electrical properties through introducing resonant states [8,26,27] and manipulating band structures, [28] suppressing thermal conductivities through introducing nanostructures, [25,[29][30][31][32] and all-scale hierarchical structures. [10,33] Among these methods, elements alloying for the solid solution with atomic-scale substitutions have been the most generally employed. Indeed, promising thermoelectric performance was achieved through simple elements alloying in the Pb-Sn-Te-Se solid solution system. [34] Similarly, extraordinary thermoelectric performance has been achieved in PbTe-PbSe, [28,35] PbTe-PbS, [36][37][38] PbTe-MTe (M = Mg, Sr), [10,33,39] PbSe-PbS, [40,41] PbSe-CdSe, and PbS-CaS solid solutions. [22,25] The above achievements in lead chalcogenides motivate us to fully investigate the thermoelectric transport properties of p-type PbTe-PbSe-PbS alloys and deeply understand this system, in which the carrier concentration was fixed with 2 mol% Na doping. Specifically, an ultrahigh power factor ≈25 µW cm −1 K −2 and a low lattice thermal conductivity ≈0.5 Wm −1 K −1 at 873 K, and thus a high ZT ≈ 1.9 are obtained in Solid solution alloying is one of the quite powerful approaches to enhance thermoelectric performance because it can simultaneously optimize electrical and thermal transport properties. Herein, a comprehensive investigation on p-type PbTe-PbSe-PbS alloys is reported, in which the carrier concentration is fixed with 2 mol% Na doping. High thermoelectric performance is achieved via synergistically tuning carrier concentration, manipulating electronic band structure, introducing nanostructures, and separating phases. Thus, a high ZT value ≈1.9 is obtained in (PbTe) 1−x (PbSe) x...

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The Atomic Circus: Small Electron Beams Spotlight Advanced Materials Down to the Atomic Scale

Cited by 29 publications

References 121 publications

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Amphoteric Indium Enables Carrier Engineering to Enhance the Power Factor and Thermoelectric Performance in n‐Type Ag_nPb₁₀₀In_nTe₁₀₀₊₂_n (LIST)

Comprehensive Investigation on the Thermoelectric Properties of p‐Type PbTe‐PbSe‐PbS Alloys

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The Atomic Circus: Small Electron Beams Spotlight Advanced Materials Down to the Atomic Scale

Cited by 29 publications

References 121 publications

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

Amphoteric Indium Enables Carrier Engineering to Enhance the Power Factor and Thermoelectric Performance in n‐Type AgnPb100InnTe100+2n (LIST)

Comprehensive Investigation on the Thermoelectric Properties of p‐Type PbTe‐PbSe‐PbS Alloys

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Amphoteric Indium Enables Carrier Engineering to Enhance the Power Factor and Thermoelectric Performance in n‐Type Ag_nPb₁₀₀In_nTe₁₀₀₊₂_n (LIST)