Characterization of the interface between an Fe–Cr alloy and the p-type thermoelectric oxide Ca3Co4O9

Abstract

of the interface between an Fe-Cr alloy and the p-type thermoelectric oxide Ca 3 Co 4 O 9 , (2013), doi: http://dx.doi.org/10. 1016/j.jallcom.2013.08.096 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Characterization of the interface between an AbstractA customized Fe-Cr alloy that has been optimized for high temperature applications in oxidizing atmospheres has been interfaced via spark plasma sintering (SPS) with a p-type thermoelectric oxide material: calcium cobaltate (Ca 3 Co 4 O 9 ). The properties of the alloy have been analyzed for its compatibility with the Ca 3 Co 4 O 9 in terms of its thermal expansion and transport properties. The thermal and electrical contact resistances have been measured as a function of temperature, and the long term electronic integrity of the interface analyzed by measuring the resistance versus time at an elevated temperature. The kinetics of the interface have been analyzed through imaging with scanning electron microscopy (SEM), elemental analysis using energy dispersive spectroscopy (EDS), and phase identification with X-ray diffraction (XRD). The results reveal the formation of an intermediate phase containing calcium and chromium in the interface that is highly resistive at room temperature, but conducting at the intended thermoelectric device hot-side operating temperature of 800°C. As the alloy is well matched in terms of its thermal expansion and highly conducting compared to the Ca 3 Co 4 O 9 , it may be further considered as an interconnect material candidate at least with application on the hot-side of an oxide thermoelectric power generation module.

Fabrication and characterization of nickel contacts for magnesium silicide based thermoelectric generators

“…EDX analysis shows that the interface layer is composed of different ternary Mg/Ni/Si phases with some Ni 31 Si 12 where we find the Sb precipitation [17].…”

“…in an SPS process. Due to its simplicity this process has been applied to several material classes [12,13]. For Mg 2 Si it has been made popular by the work of Japanese groups, who have also shown Mg 2 Si based thermoelectric generators [9,[14][15][16][17].…”

Segmented Thermoelectric Oxide‐Based Module for High‐Temperature Waste Heat Harvesting

“…Figure 4a,b plots the temperature dependence of the contact resistanceb etween the Ag electrodes with pCa349a nd n-Zn 0.98 Al 0.02 O. Thei nterfacial microstructure is presented through SEM images in the inset-figures.T he Ag electrodes and the oxide materials have ag ood connection at the interface.S canninge lectron microscopy (SEM) and energyd ispersive X-ray spectroscopy (EDS) analyses revealedt hat there are no obviousd iffusion and secondary phaseso bserved in the vicinityo ft hose joints.C onsequently, the obtained contact resistancev aluesw ere measured to be approximately 400 mW cm À2 ,w hich are lower than the electrode using Fe22Cr. [25] Figure 4c illustrates the contactr esistance of segmented HH/Ag/Ca349. Thec ontact resistance tends to decrease from 170 mW cm À2 at room temperature to 100 mW cm À2 at 1000 K. Measurement of the contact resistance of the interface between HH and the Ag electrodea t room temperature showedt hat the contact resistance was as small as 5 mW cm À2 .A spresented in Figure 4c,t he interfacial resistance exhibited an abrupt changei ni ts temperature dependence at approximately 600 K. This might be associated with afirst-order transition of Ca 3 Co 4 O 9 + d .…”

“…Thec ontact resistance tends to decrease from 170 mW cm À2 at room temperature to 100 mW cm À2 at 1000 K. Measurement of the contact resistance of the interface between HH and the Ag electrodea t room temperature showedt hat the contact resistance was as small as 5 mW cm À2 .A spresented in Figure 4c,t he interfacial resistance exhibited an abrupt changei ni ts temperature dependence at approximately 600 K. This might be associated with afirst-order transition of Ca 3 Co 4 O 9 + d . [25] Thep ower generation of the module is expected to improve by using segmented legs,a sp redicted in the modeling part. However, under realistic working conditions there are many factorst hat affect the output power of modules,s uch as heat losses,c ontactr esistances,h eat transfer,e tc.…”

Effects of conducting oxide barrier layers on the stability of Crofer® 22 APU/Ca3Co4O9 interfaces

“…A more careful analysis of the interfacial contact resistance was carried out on samples cut from the leftover pieces of the layered pellets using a custom system described elsewhere. 5 Analysis of the microstructure and composition at the interfaces was performed using a TM3000 scanning electron microscopy (SEM) from Hitachi (Tokyo, Japan) equipped with a Bruker SDD EDS detector (Billerica, MA).…”