The beneficial effect of Fe addition in PbTe-Ni diffusion bonded thermoelectric contact interfaces – A comprehensive phase evolution study

Kumar, D and Muse, CA and Femi, OE and Ravishankar, N and Chattopadhyay, K (2023) The beneficial effect of Fe addition in PbTe-Ni diffusion bonded thermoelectric contact interfaces – A comprehensive phase evolution study. In: Acta Materialia, 261 .

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Abstract

The development of reliable interconnects in thermoelectric (TE) modules is essential for the durability and serviceability of these solid-state devices. PbTe-based devices are used in mid-temperature range applications, with Ni being the most preferred interconnect. Ni reacts with PbTe to form a binary intermetallic, Ni3Te2 (β2). The sustained growth of this phase at higher service temperatures is adversarial to the long-term reliability of interconnects. This paper reports and discusses the beneficiary role of minor Fe-addition in the Ni contact alloy to arrest such unwarranted chemical interaction while ensuring proper bonding. PbTe and Ni-Fe (Fe = 1 at.%, 5 at.%) discs are diffusion bonded at 700 °C for various holding times. The current investigation leads to three noteworthy observations: 1) the formation of Fe-enriched Ni-Fe phase islands at the interface at microscale (1 - 10 µm), (2) Fe-segregation at the local interfaces (∼ 10 nm), and (3) the growth of a Ni-rich metastable Ni3-xTe phase, not present in Ni-Te binary phase diagram. Detailed examinations of these phenomena and crystallographic relations (β2 and Ni3-xTe) are conducted through advanced analytical TEM/STEM techniques. Furthermore, the PbTe-Ni reaction formulation is modified to accommodate such a Fe-enrichment phenomenon and is validated through free energy calculations. © 2023 Acta Materialia Inc.

Item Type:	Journal Article
Publication:	Acta Materialia
Publisher:	Acta Materialia Inc
Additional Information:	The copyright for this article belongs to the Acta Materialia Inc.
Keywords:	Binary alloys; Chemical bonds; Diffusion; Iron alloys; IV-VI semiconductors; Lead alloys; Lead compounds; Nickel alloys; Phase interfaces, ABF imaging; Contact electrode pbte; Contact electrodes; Fe enrichment; Fe interstitial; HAADF; Interstitials; Metastable ni3-xte; Metastables; Ni; TEM; Thermoelectric; Thermoelectric contact; Thermoelectric devices, Free energy
Department/Centre:	Division of Chemical Sciences > Materials Research Centre Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	15 Dec 2023 11:09
Last Modified:	15 Dec 2023 11:09
URI:	https://eprints.iisc.ac.in/id/eprint/83355

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