Cost Efficient Manufacturing of Silicide Thermoelectric
Materials and Modules using RGS Technique
(b)
A.
1
Schönecker ,
1
Kraaijveld ,
2
Til ,
3
Brinks ,
B.
A. E. van
P.
2
3
1
A. J. Böttger , M.Huijben , M. den Heijer
1RGS
Development B.V., Bijlestaal 54a, 1721 PW Broek op Langedijk, The Netherlands
2Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
3MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
INTRODUCTION
To harvest the promise of thermoelectric (TE) power generation at higher temperatures in
the area of industrial waste heat recovery a number of challenges must be met:
- TE system requirements
-
Financial return of investment period of less than 3 years
No disturbance of industrial manufacturing process
Environmentally benign, low maintenance system
CHROMIUM DOPED HIGHER MANGANESE SILICIDES (HMS)
Samples
Material composition (%wt.)
Si
Mn
52%
48%
50.2%
47.3%
48.1%
39.4%
75-8NA, 75-10NA
76-9NA, 76-10NA
77-8NA, 77-10NA
MnSi1.74
Cr0.05Mn0.95Si1.74
Cr0.25Mn0.75Si1.74
Structure
- TE module requirements
-
Cr
0%
2.5%
12.5%
Modules for high temperature application
Module design adaptable to system requirements
-TE material requirements
-
Lowest cost, stable, environmentally benign materials
Reasonable ZT values
OBJECTIVES AND APPROACH
The objective is to develop thermoelectric materials and modules that can be used in high
temperature industrial waste heat recovery applications.
By the use of the ribbon-growth-on-substrate (RGS) casting process:
- To produce thermoelectric legs in a low cost, single step process;
- With stable and proven silicide compositions;
- In a flexible net shape format.
By development of a low cost TE module concept that:
- Operates in a high T environment (T > 500oC);
- Can be manufactured easily;
- Allows versatile module design to meet system requirements.
XRD spectrum and SEM cross sections of HMS samples with 0%, 2.5wt%, and 12.5wt% Cr.
While lower Cr concentrations (a), (b) only show a Si and a HMS phase, the 12.5wt% Cr
sample (c) also shows a CrSi2 phase.
TE Characteristics
MATERIAL AND MODULE MANUFACTURING
A Single Step TE Leg Casting
Sample
k [W/(m·K)] at T=300K
75-10NA
2.20
MnSi1.74
76-9NA
3.33
Cr0.05Mn0.95Si1.74
77-8NA
3.35
Cr0.25Mn0.75Si1.74
Comparison with Literature Values
Sample
RGS technique replaces multiple material manufacturing steps by a single step direct casting process.
Strip Based TE Module Manufacturing
(a)
(b)
[1]
[2]
75-10NA
[1]
[1]
76-10NA
[2]
[2]
77-8NA
Cr at%
ZTmax
TZTmax [K]
S [mV/K]
0
0.36
0.28
0.26
0.6
0.56
0.46
0.39
0.52
0.51
850
900
825
850
850
883
900
900
883
190
250
258
200
200
227
180
150
159
0.03
0.05
0.10
0.20
0.25
s [S/cm] k [W/(m·K)]
312
200
117
455
455
338
280
580
655
2.9
3.5
2.5
2.5
2.7
3.3
3
3
3.5
MnSi1.74
Cr0.03Mn0.97Si1.74
Cr0.05Mn0.95Si1.74
Cr0.10Mn0.90Si1.74
Cr0.20Mn0.80Si1.74
Cr0.25Mn0.75Si1.74
CONCLUSIONS
RGS material casting technology:
- is an ideal platform to produce metal silicide TE materials in net-shape form.
- is low cost, industrial scale, single step process.
- is capable of producing HMS materials with competitive ZT values.
In combination with a low-cost, strip based TEG module concept for high temperature
industrial waste heat recovery, a strong cost reduction for TE power generation is possible.
REFERENCES
Net shape strip casting of RGS materials (a). Conceptual design of the active components of a TEG
module made from strip shaped legs. (b) Thermal module concept to test operation temperature and
material stability.
[1] Y. Miyazaki, Y. Saito, K. Hayashi, K. Yubuta, and T. Kajitani, Japanese Journal of
Applied Physics, Vol. 50, p. 035804, 2011
[2] Y. Kikuchi, Y. Miyazaki, Y. Saito, K. Hayashi, K. Yubuta, and T. Kajitani, Japanese Journal
of Applied Physics, Vol. 51, pp. 1–5, 2012