Here we report on technical details of preparation of Si-Ge-based nanostructured thermoelectic materials
by a mechnical alloying method. It has been shown that for a milling speed of 350 rpm a single Si-Ge
phase is formed after milling time less than 6 h.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3530

Gorshenkov, M.

Kaloshkin, S.

Khovaylo, V.

Usenko, A.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 4, 04NEA15(2pp) (2012)   2304-1862/2012/1(4)04NEA15(2) 04NEA15-1  2012 Sumy State University Optimization of Ball-Milling Process for Preparation of Si-Ge  Nanostructured Thermoelectric Materials  V. Khovaylo*, M. Gorshenkov, S. Kaloshkin, A. Usenko  National University of Science and Technology “MISiS”, 119049 Moscow, Russia  (Received 26 June 2012; published online 08 August 2012)  Here we report on technical details of preparation of Si-Ge-based nanostructured thermoelectic mate-rials by a mechnical alloying method. It has been shown that for a milling speed of 350 rpm a single Si-Ge phase is formed after milling time less than 6 h.  Keywords: Mechanical Alloying, Thermoelectricity, Si-Ge, Nanostructure.   PACS numbers: 79.10.N – , 61.46.Df                                                             * khovaylo@misis.ru 1. INTRODUCTION  It has been recognized recently that the bulk nanostructuring approach provides a route for the reliable improvement in the performance of thermoelectric materials (see for recent review Ref. [1]). A marked increase in the figure-of-merit ZT has been reported for materials with nanoscaled grain size. The increase of ZT is mainly attributed to a reduction in thermal conductivity due to the enhanced phonon scattering at the grain boundaries. Method of mechanical alloying is particularly suitable for the preparation of a large quantity of nanostructured thermoelectric materials with superior, as compared to single- or polycrystalline analogues, thermoelectric properties. For example, considerable progress has recently been made in improving thermoelectric properties of p-type as well as n-type Si-Ge materials [2,3]. However, reported in the papers technical details of the ball-milling process are often cursory [3]. Here we report on the evolution of structural properties of n-type Si-Ge thermoelectric materials during ball-milling.  2. EXPERIMENTAL DETAILS  The materials were prepared from powders of high-purity (better than 99.999%) Si, Ge, and P by a Fritsch planetary mill using stainless steel vial and balls at milling speed up to 350 rpm and milling time up to 18 h. Crystal structure of the Si-Ge powdered samples was checked by a Rigaku Ultima x-ray diffractometer (XRD) whereas microstructure and chemical composition were identified by transmission and scanning electron microscopy (TEM and SEM, respectively).  3. EXPERIMENTAL RESULTS  In order to track evolution of the crystal structure of the studied alloys, and determine optimal parame-ters of the milling, we varied milling speed and mill-ing time. The milling speed varied from 250 to 350 rpm whereas milling time varied from 1 to 18 h. XRD examination revealed that in the case of mill-ing speed 250 rpm the solid solution of Si-Ge is formed after milling time 12 h. However, chemical characterization of the sample by an Energy Disper-sive X-ray Spectroscopy (EDX) showed that the sam-ple is contaminated by a sizable (around 1 at.%) amount of Fe which is a consequence of the use of stainless steel vial and balls. In order to eliminate Fe contamination, a high milling speed was used in fur-ther experiments. Results of the x-ray diffraction measurements revealed that for a milling speed of 350 rpm a single phase Si-Ge was formed after milling time less than 6 h (Fig. 1). The mean size of crystallites estimated from the XRD data by a Williamson – Hall method was found to be of about 10 nm and decreases with the increase in the milling time.    Fig. 1 – X-ray diffraction patterns of Si80Ge20P2, prepared by mechanical alloying at a milling speed 350 rpm  Powdered Si-Ge sample prepared by mechanical alloying at a speed of 350 rpm for milling time 6 h was further characterized by the TEM and SEM   V. KHOVAYLO, M. GORSHENKOV, S. KALOSHKIN, A. USENKO PROC. NAP 1, 04NEA15 (2012)   04NEA15-2  Fig. 2 – Transmission electron microscopy images of Si80Ge20P2 mechanically alloyed at a milling speed 350 rpm for 6 h techniques. It was seen from TEM pictures that the  crystallites in the as-prepared powder agglomerate in larger particles with an average size below 200 nm (Fig. 2). All these results are in a good agreement with those published by Wang et al. [3].  4. SUMMARY  It has been shown that Si-Ge nanostructured materials with the mean crystallite size of about 10 nm can be prepared by mechanical alloying of the raw ingredients for 6 h at a milling speed of 350 rpm.      REFERENCES  1. Y. Lan, A.J. Minnich, G. Chen, and Z. Ren, Adv. Funct. Mater. 20, 357 (2010). 2. G. Joshi et al., Nano Lett. 8, 4670 (2008). 3. X. W. Wang, et al., Appl. Phys. Lett. 93, 193121 (2008).  

Optimization of Ball-Milling Process for Preparation of Si-Ge Nanostructured Thermoelectric Materials

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 4, 04NEA15(2pp) (2012) 
 
 
2304-1862/2012/1(4)04NEA15(2) 04NEA15-1  2012 Sumy State University 
Optimization of Ball-Milling Process for Preparation of Si-Ge  
Nanostructured Thermoelectric Materials 
 
V. Khovaylo*, M. Gorshenkov, S. Kaloshkin, A. Usenko 
 
National University of Science and Technology “MISiS”, 119049 Moscow, Russia 
 
(Received 26 June 2012; published online 08 August 2012) 
 
Here we report on technical details of preparation of Si-Ge-based nanostructured thermoelectic mate-
rials by a mechnical alloying method. It has been shown that for a milling speed of 350 rpm a single Si-Ge 
phase is formed after milling time less than 6 h. 
 
Keywords: Mechanical Alloying, Thermoelectricity, Si-Ge, Nanostructure. 
 
 PACS numbers: 79.10.N – , 61.46.Df 
 
 
                                                          
* khovaylo@misis.ru 
1. INTRODUCTION 
 
It has been recognized recently that the bulk 
nanostructuring approach provides a route for the 
reliable improvement in the performance of 
thermoelectric materials (see for recent review Ref. 
[1]). A marked increase in the figure-of-merit ZT has 
been reported for materials with nanoscaled grain 
size. The increase of ZT is mainly attributed to a 
reduction in thermal conductivity due to the enhanced 
phonon scattering at the grain boundaries. 
Method of mechanical alloying is particularly 
suitable for the preparation of a large quantity of 
nanostructured thermoelectric materials with 
superior, as compared to single- or polycrystalline 
analogues, thermoelectric properties. For example, 
considerable progress has recently been made in 
improving thermoelectric properties of p-type as well 
as n-type Si-Ge materials [2,3]. However, reported in 
the papers technical details of the ball-milling process 
are often cursory [3]. Here we report on the evolution 
of structural properties of n-type Si-Ge thermoelectric 
materials during ball-milling. 
 
2. EXPERIMENTAL DETAILS 
 
The materials were prepared from powders of 
high-purity (better than 99.999%) Si, Ge, and P by a 
Fritsch planetary mill using stainless steel vial and 
balls at milling speed up to 350 rpm and milling time 
up to 18 h. Crystal structure of the Si-Ge powdered 
samples was checked by a Rigaku Ultima x-ray 
diffractometer (XRD) whereas microstructure and 
chemical composition were identified by transmission 
and scanning electron microscopy (TEM and SEM, 
respectively). 
 
3. EXPERIMENTAL RESULTS 
 
In order to track evolution of the crystal structure 
of the studied alloys, and determine optimal parame-
ters of the milling, we varied milling speed and mill-
ing time. The milling speed varied from 250 to 350 
rpm whereas milling time varied from 1 to 18 h. 
XRD examination revealed that in the case of mill-
ing speed 250 rpm the solid solution of Si-Ge is 
formed after milling time 12 h. However, chemical 
characterization of the sample by an Energy Disper-
sive X-ray Spectroscopy (EDX) showed that the sam-
ple is contaminated by a sizable (around 1 at.%) 
amount of Fe which is a consequence of the use of 
stainless steel vial and balls. In order to eliminate Fe 
contamination, a high milling speed was used in fur-
ther experiments. 
Results of the x-ray diffraction measurements 
revealed that for a milling speed of 350 rpm a single 
phase Si-Ge was formed after milling time less than 6 
h (Fig. 1). The mean size of crystallites estimated 
from the XRD data by a Williamson – Hall method 
was found to be of about 10 nm and decreases with 
the increase in the milling time. 
 
 
 
Fig. 1 – X-ray diffraction patterns of Si80Ge20P2, prepared by 
mechanical alloying at a milling speed 350 rpm 
 
Powdered Si-Ge sample prepared by mechanical 
alloying at a speed of 350 rpm for milling time 6 h 
was further characterized by the TEM and SEM  
 V. KHOVAYLO, M. GORSHENKOV, S. KALOSHKIN, A. USENKO PROC. NAP 1, 04NEA15 (2012) 
 
 
04NEA15-2 
 
Fig. 2 – Transmission electron microscopy images of Si80Ge20P2 
mechanically alloyed at a milling speed 350 rpm for 6 h 
techniques. It was seen from TEM pictures that the  
crystallites in the as-prepared powder agglomerate in 
larger particles with an average size below 200 nm 
(Fig. 2). All these results are in a good agreement with 
those published by Wang et al. [3]. 
 
4. SUMMARY 
 
It has been shown that Si-Ge nanostructured 
materials with the mean crystallite size of about 10 nm 
can be prepared by mechanical alloying of the raw 
ingredients for 6 h at a milling speed of 350 rpm. 
 
 
 
 
 
REFERENCES 
 
1. Y. Lan, A.J. Minnich, G. Chen, and Z. Ren, Adv. Funct. 
Mater. 20, 357 (2010). 
2. G. Joshi et al., Nano Lett. 8, 4670 (2008). 
3. X. W. Wang, et al., Appl. Phys. Lett. 93, 193121 (2008).
 
 


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Optimization of Ball-Milling Process for Preparation of Si-Ge Nanostructured Thermoelectric Materials

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