Reversible structural transition in spark plasma-sintered thermoelectric Zn4Sb3

In Situ TEM Studies of Nanostructured Thermoelectric Materials: An Application to Mg‐Doped Zn4Sb3 Alloy

“…[38,48] Our observations indicate that no decomposition process occurred at temperatures below 673 K, as suggested in an umber of previous studies. [38,48] Our observations indicate that no decomposition process occurred at temperatures below 673 K, as suggested in an umber of previous studies.…”

“…Formation and growth of the secondary trigonal/hexagonal phase in the matrix of the primary Zn 6 Sb 5 phase could be ascribed to the movement and/or self-diffusion of Zn interstitial from the nonstoichiometric counterpart in the material. [38,48] Our observations indicate that no decomposition process occurred at temperatures below 673 K, as suggested in an umber of previous studies. [20,36,37] The origin of the movement and self-diffusion is the high mobility of Zn atoms, whichh as been knownasahigh superionic conductor.…”

“…The compositionally single-phasenature of the primary phase in Figure 5a is also supported by the uniform distribution of Mg, Zn and Sb elements in STEM-EDX maps of such elements (Supporting Information,S4). [38,48] In the Zn 4 Sb 3 structure, there are 18 Sb 3À and 12 Sb 2À ions per unit cell, corresponding to total of 78 negative charges. The enrichment results in an average atomicw eight lower than the matrix region and, as a result, causes darker contrasti nt he STEM-HAADF ( Figure 6a).…”

“…[1] Nanocomposites with enhanced zT have been found in the various TE material families, including Bi 2 Te 3 -based nanocomposites, [5][6][7][8] PbTe-based nanostructured materials, [9][10][11] SiGe-based nanocomposites, [12][13][14][15] and ZnSb alloys, [16][17][18][19][20] etc. [17,[28][29][30][31][32][33][34][35][36] TheZ n 4 Sb 3 was also proposed to decompose into ZnSb and Zn, [21,[36][37][38] but this hypothesisw as only supported by indirect experimental work, for example, TE characterization in different conditions and high-temperature powder X-ray diffraction, [17,23] which could only give very limited understanding of the processes at atomic scales. In addition, Zn 4 Sb 3 consists of low-costa nd abundant elements; hence,i th as been considered as one of the best p-type candidates for making al ow-cost and high-conversion-efficiency thermoelectric powerg enerators (TEG).…”

“…Such nanostructures strongly enhances phonon scattering, resulting in ad ecreasei nt he thermal conductivity leading to a zT value of 1.4 at 718 K. of Zn 4 Sb 3 have proposed migration of high dynamic Zn into Zn interstitial (hcp)s ites at elevated temperature as the main mechanism of Zn 4 Sb 3 degradation. [17,[28][29][30][31][32][33][34][35][36] TheZ n 4 Sb 3 was also proposed to decompose into ZnSb and Zn, [21,[36][37][38] but this hypothesisw as only supported by indirect experimental work, for example, TE characterization in different conditions and high-temperature powder X-ray diffraction, [17,23] which could only give very limited understanding of the processes at atomic scales. There remained an umber of limitations:i )the explanation relied on experimental resultsc ollected from different typeso fs tudied sample;t hat is, powder materialsf or XRD and pressed pellet for TE characterization;i i) the test conditions of Zn 4 Sb 3 materials was not equivalent to the TE conditions (i.e.…”