Dynys, F.

Mackey, J.

Sayir, A.

Sehirlioglu, A.

NASA Technical Reports Server

I • l 
Composite Silidde Tllermodedric Materials tor Power 
Geaeration 
F. Dynys1, J. Mackey", A Sebirlioglu2 &A Sayir1 
'NASA Glmn ~Cit~ Cleveland, Ohio. USA 
>esse Westem1teoa¥eUnivasity. Clcvelan 0100. USA 
3£Iniv<cit)'oCAkroa. AknJo. Ohio. !JSA 
TE Materials 
TE - Si/Ge Alloys, Silicides, Ceramics 
Temperature Range - 500 - l 000 "C 
Enviroomeot -~NO,., CO,~ ~0 
• Phonon Scattering 
• Nano inclusions 
-J185aiJ(N o 
• Alloyed Si/Ge matrix 
• Mingo et al. 
% · 5 · /o · 1's • :JD 
""""f""'ilc diunct<r (amJ 
MingoN,ctal. ''Nanopatide-in-AIIoy-,Nano 
./LtNn,9(2009), 711-71.5 
• 2-l 0 nm -optimum size 
• WSiz Best Sificide! 
Si-TiSiJ(S~Ge)-TiSi2 
_.,. ....... 
__ .,.,... 
..... !··~ 
--
. 1 .. TI 
,. .. 
.. .. 
[•r-------~~-.,r~ 
W •~--------------~~ 
6/14/2012 
Power Generation 
Vehicle ~)stems Safety T«hnologies 
\\nles!~---. 
bo:Ji!<>ilil"""*'Jn:an. 
~ 
·' -
~,= '';' 
/~· 
P~nmetef 
Tempera lUre 1525"C 
e 
Melt -Solidification 
Advant~es 
-stable High Temperature 
hiierfaceS Grow1h Rate 50-300 mm/min 
otJaiquc miaostruclures 
~hderfaces 
~ ........ Sl 
-
Temp Gradient 
Hea1ing Rate 
Tune 
CNclble 
850C/em 
10-20 'Chnln 
5-20 Hours 
Boron Nitride 
Glassy Cerbon 
Si02 +Caa, 
._._,...,._,......,,._ Si-TiSi/(Si,Ge}-TiSi2 
Solidification Microstructures 
25%Ti/0-1% Ge .... 5%Ge 100/oGe 
.. W .§ .. -~(Ill \1 I. ~ .. 
;: :~ 
... -
. . 
-nasagcw . 
1 
https://ntrs.nasa.gov/search.jsp?R=20150010326 2019-08-31T08:05:49+00:00Z
Melt Derived WSi2-SUGe 
Resistivity Seebeck 
... '1..,. 
... 
. .. 
., . .. 
,. . .., 
* *t * ..... 
~ · . . 
\ * o ~o ! oD~.f.t% 
... •:0 oD ~ 0 ~ ~a,S,Bo 
o o • • sssllsB'/, ,...,, ...... 
"l--.-, -:<>-!tl:::-!;:..a_:~s--~- -~-~-~-,-.--j-
·. 
- ,_sw;. 
-.rcJ 
c;.contant 
,...,., ... 
I -Higher n>Sistivily at4-S% Go I 
-Lowe< resistivity attS-25% Go 
•Higher Seebeck voltages at 4-8% Go 
•Lowe< Seebeck volatages attS-25% Go 
Power Factor 
Melt Derived WSi2-Si/Ge Melt Derived MoSI2.Si/Ge 
·-· 0 S1IGHIIoS, 
Temp. f>q 
•Large power fuctors > nano SifGe 
•High power fuctors at low temperatures 
•High power factors at lower Ge content 
Spark Plasma Sintering 
Parameter I Value 
Temperature 800-1100 ·c 
Heating.Cooling Rate ZOO "Cimln 
Applied Pressure 70-90 MPa 
Hold lime -10min 
,_.___,..,_._ (Si,Ge)-MoS~ 
Si--Mo.~ 200 mmlhr 
Seebeck Resistivity 
=~·············.·· -~ · -- ·- . i~ :~~~::: ~ ::::_~=.=.:~:~:=--
~= .-·- 1 -·-. i ~ .-_./ ---- . P,f'O-..-
·-----
Thermal Conductivity 
~~~ 
---•tta(~_;,. 
---n'fA;IIu 
_ .....,., 
~~ &.Si-WSiz-High 1C 
o(ie .imponanl in .reducing " 
•SH\1oSi1 more dependent on 
Ge contenl than Si-WSi2 
6/14/2012 
Temp. (•C) 
•Si-WSi2 system g ives ZT of 0.6 
Temp. (OC) 
WSi2-Si/Ge 
•Further reduction in 1C will 
eobanceZT 
Meh Solidification vs Sparlc. Plasma Sintering 
9%Gei1%W 
2 
Si/Ge-WS~ 
Meh Solidification vs Spark Plasma Sintering 
9%Ge/1%W 
Previous New 
Summary 
W ,Mo & Ti systems gave high power factors (more than twice 
the nano-Si/Ge). 
W ,Mo & Ti -large power- factors allow temperatun~s. 
ZT = 0.55 for WSiz-SiiGe eutectic is demonstrated. 
WSirSi!Ge- Potential higher ZT- reducing thermal conductivity 
SPS - Have not achieve good TE properties 
~~~_.~~ 
Spark Plasma Sintering P-Type 
Si/Ge/W 1100 "C 10 min 35 KN 
1nbomogeneity 
lCP - {lzContent - l-3 Wt.% 
.-
"" -
Melt Processed 
Si/9%Geii%W 
§ » ~ . ' . , ' , ___ ~ ···-
·- ' ~ ~ . -.1 . . . ~-.:...:.-· . 
ICP - Chemical Analysis Si/Ge ~1.1 
--
10 Od 
6/14/2012 
-.nasag<H .. 
3 


Composite Silicide Thermoelectric Materials for Power Generation

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