Bridging the miscibility gap towards higher thermoelectric performance of PbS

1985 ◽

Vol 43 ◽

pp. 70-71

Author(s):

M.G. Burke ◽

M.K. Miller

Keyword(s):

Low Temperature ◽

Microstructural Characterization ◽

Superlattice Reflection ◽

High Volume ◽

Atom Probe ◽

Dark Field ◽

Miscibility Gap ◽

Second Phase ◽

Two Phase ◽

Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

Download Full-text

Transition alpha structure in beta-isomorphous Nb-Hf alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126068 ◽

1987 ◽

Vol 45 ◽

pp. 232-233

Author(s):

R.W. Carpenter ◽

Changhai Li ◽

David J. Smith

Keyword(s):

Solid Solution ◽

Solution Phase ◽

Miscibility Gap ◽

Large Strains ◽

Solid Solution Phase ◽

Two Phase ◽

Diffuse Intensity ◽

Metastable Form ◽

The Matrix ◽

Equilibrium Morphology

Binary Nb-Hf alloys exhibit a wide bcc solid solution phase field at temperatures above the Hfα→ß transition (2023K) and a two phase bcc+hcp field at lower temperatures. The β solvus exhibits a small slope above about 1500K, suggesting the possible existence of a miscibility gap. An earlier investigation showed that two morphological forms of precipitate occur during the bcc→hcp transformation. The equilibrium morphology is rod-type with axes along <113> bcc. The crystallographic habit of the rod precipitate follows the Burgers relations: {110}||{0001}, <112> || <1010>. The earlier metastable form, transition α, occurs as thin discs with {100} habit. The {100} discs induce large strains in the matrix. Selected area diffraction examination of regions ∼2 microns in diameter containing many disc precipitates showed that, a diffuse intensity distribution whose symmetry resembled the distribution of equilibrium α Bragg spots was associated with the disc precipitate.

Download Full-text

Hierarchical structures lead to high thermoelectric performance in Cum+nPb100SbmTe100Se2m (CLAST)

Energy & Environmental Science ◽

10.1039/d0ee03459b ◽

2021 ◽

Author(s):

Siqi Wang ◽

Yu Xiao ◽

Yongjin Chen ◽

Shang Peng ◽

Dongyang Wang ◽

...

Keyword(s):

Hierarchical Structures ◽

Phonon Transport ◽

Thermoelectric Performance

Hierarchical microstructures lead to high thermoelectric performance in Cum+nPb100SbmTe100Se2m (CLAST) through synergistically optimizing carrier and phonon transport.

Download Full-text

Optimization of sodium hydroxide for securing high thermoelectric performance in polycrystalline Sn 1 − x Se via anisotropy and vacancy synergy

InfoMat ◽

10.1002/inf2.12057 ◽

2019 ◽

Vol 2 (6) ◽

pp. 1201-1215 ◽

Cited By ~ 7

Author(s):

Xiao‐Lei Shi ◽

Wei‐Di Liu ◽

Ang‐Yin Wu ◽

Van T. Nguyen ◽

Han Gao ◽

...

Keyword(s):

Sodium Hydroxide ◽

Thermoelectric Performance

Download Full-text

Novel Co-Cu-Based Immiscible Medium-Entropy Alloys with Promising Mechanical Properties

Metals ◽

10.3390/met11020238 ◽

2021 ◽

Vol 11 (2) ◽

pp. 238

Author(s):

Sujung Son ◽

Jongun Moon ◽

Hyeonseok Kwon ◽

Peyman Asghari Rad ◽

Hidemi Kato ◽

...

Keyword(s):

Mechanical Properties ◽

Binary System ◽

Design Methodology ◽

Miscibility Gap ◽

Face Centered Cubic ◽

Solid Solution Strengthening ◽

Solution Strengthening ◽

Face Centered ◽

Strength And Ductility ◽

Cobalt Copper

New AlxCo50−xCu50−xMnx (x = 2.5, 10, and 15 atomic %, at%) immiscible medium-entropy alloys (IMMEAs) were designed based on the cobalt-copper binary system. Aluminum, a strong B2 phase former, was added to enhance yield strength and ultimate tensile strength, while manganese was added for additional solid solution strengthening. In this work, the microstructural evolution and mechanical properties of the designed Al-Co-Cu-Mn system are examined. The alloys exhibit phase separation into dual face-centered cubic (FCC) phases due to the miscibility gap of the cobalt-copper binary system with the formation of CoAl-rich B2 phases. The hard B2 phases significantly contribute to the strength of the alloys, whereas the dual FCC phases contribute to elongation mitigating brittle fracture. Consequently, analysis of the Al-Co-Cu-Mn B2-strengthened IMMEAs suggest that the new alloy design methodology results in a good combination of strength and ductility.

Download Full-text