Malaysian Journal of Analytical Sciences Vol 20 No 5 (2016): 1001 - 1010

DOI: http://dx.doi.org/10.17576/mjas-2016-2005-04

 

 

 

OPTIMIZATION PARAMETER FOR THERMOELECTRIC PROPERTIES OF ZnO USING RESPONSE SURFACE METHODOLOGY

 

(Pengoptimuman Parameter Untuk Sifat Termoelektrik ZnO Menggunakan

Kaedah Gerak Balas Permukaan)

 

Lim Joon Hoong*, Yeoh Cheow Keat, Abdullah Chik, Teh Pei Leng

 

School of Materials Engineering,

Universiti Malaysia Perlis, 02600 Jejawi, Perlis, Malaysia

 

*Corresponding author: jhlim07@gmail.com

 

 

Received: 5 January 2016; Accepted: 23 May 2016

 

 

Abstract

The effect of Al dopants and sintering temperature on thermoelectric properties of ZnO was studied using the response surface method. The design of experimental work was performed with the response surface method used to determine the significant level of factors which are sintering temperature in the range of 800 – 1000 °C and Al dopants in the range of 0 – 4 wt.%. The thermoelectric properties of Al-doped ZnO were enhanced with increasing Al dopants and slightly decreased when increasing sintering temperature. Additional phase ZnAl₂O₄ was detected for 3 wt.% and 4 wt.% Al-doped ZnO pellets as the sintering temperature increased to 1000 °C. The presence of ZnAl₂O₄ phase slightly decreased the electrical conductivity compared to single ZnO phase samples. The optimum parameter values for this study was Al dopant (4 wt.%) and sintering temperature (800 °C). The effect of Al doping to the band structure of ZnO was studied using first-principles based on density functional theory (DFT). The calculated band structure of ZnO and Al doped ZnO shows that ZnO is a direct band gap semiconductor. The calculated band gap of ZnO (0.749 eV) become smaller with the concentration of Al doping increased to 4 wt.% (0.551 eV). The trend of the calculated band gap of Al-doped ZnO was in agreement with the electrical conductivity test results which increased with increasing Al content. However, it must be noted that the software predictions do not take into account the presence of additional ZnAl₂O₄ phases. The presence of these extra phases may lead to even lower electrical conductivity.

 

Keywords:    Al-doped ZnO, response surface method, sintering temperature, thermoelectric, electronic band structure

 

Abstrak

Kesan Al dop dan suhu pembakaran ke atas termoelektrik ZnO dikaji dengan menggunakan kaedah gerak balas permukaan. Reka bentuk kerja eksperimen telah dilakukan dengan kaedah gerak balas permukaan untuk menentukan aras signifikan suhu pembakaran pada julat 800 – 1000 °C dan Al dop dalam lingkungan 0 – 4% berat. Sifat – sifat termoelektrik Al-dop ZnO telah dipertingkatkan dengan peningkatan Al dop dan pensinteran suhu. Fasa tambahan ZnAl₂O₄ dikesan bagi 3% berat dan 4% berat Al-dop ZnO bila suhu pembakaran meningkat daripada 800 °C hingga 1000 °C. Kekonduksian elektrik menurun dengan kehadiran fasa ZnAl₂O₄ berbanding sampel fasa ZnO tunggal. Nilai – nilai parameter optimum untuk kajian ini adalah Al pendopan (4% berat) dan suhu pensinteran (800 °C). Kesan Al doping kepada struktur jalur ZnO dikaji menggunakan prinsip pertama berdasarkan teori fungsi ketumpatan. Struktur jalur yang dikira pada ZnO dan Al dop ZnO menunjukkan bahawa ZnO adalah semikonduktor jurang jalur terus. Dengan Al dop, jurang jalur ZnO (0.749 eV) menjadi lebih kecil dengan peningkatan kepekatan Al dop pada 4 wt.% (0.551 eV). Trend jurang jalur yang dikira pada ZnO Al-didopkan adalah selari dengan keputusan ujian kekonduksian elektrik yang meningkat dengan peningkatan kandungan Al. Walau bagaimanapun, ia perlu diambil perhatian bahawa ramalan perisian tidak mengambil kira kehadiran fasa ZnAl₂O₄ tambahan. Kehadiran kedua – fasa tambahan boleh membawa kepada kekonduksian elektrik yang lebih rendah.

 

Kata kunci:  Al dop ZnO, kaedah gerak balas permukaan, suhu pembakaran, termoelektrik, struktur jalur elektronik

 

References

1.       Tritt, T. M. (2011). Thermoelectric phenomena, materials, and applications. Annual Review of Materials Research, 41(1):433 – 448.

2.       Cheng, H., Xu, X. J., Hng, H. H. and Ma, J. (2009). Characterization of Al-doped ZnO thermoelectric materials prepared by RF plasma powder processing and hot press sintering. Ceramics International, 35(8):3067 – 3072.

3.       Goldsmid, H. (2010). Application of the transverse thermoelectric effects. Journal of Electronic Materials, 1:1 – 6.

4.       Huang, M. H., Mao, S., Feick, H., Yan, H., Wu, Y., Kind, H., Weber, E., Russo, R. and Yang. P. (2001). Room-temperature ultraviolet nanowire nanolasers. Science, 292:1897 – 1899.

5.       Ried, R. P., Kim, E., Hong, D. M. and Muller, R. S. (1993). Piezoelectric microphone with on-chip CMOS circuit. Journal of Microelectromechanical Systems, 2: 111 – 120.

6.       Ito, Y., Kushida, K., Sugawara, K. and Takeuchi, H. (1995). A 100-Mhz ultrasonic transducer array using ZnO thin films. IEEE Transaction on Ultrasonic, Ferroelectric and Frequency Control, 42: 316 – 323.

7.       Burdett, J. K., Price, G. D. and Price, S. L. (1982). Role of the crystal field theory in determining the structures of spinels. Journal of the American Chemical Society, 104(1): 92 – 95.

8.       Yan, X. D., Han, J., Chen, R. Q., Gao, W., Metson, J. and Zou., C. W. (2009). Study of a nitrogen-doped ZnO film with synchrotron radiation. Applied Physics Letters, 94: 171903.

9.       Jimenez-Gonzalez, A. E., Jose A., Urueta, S. and Suarez-Parra, R. (1998). Optical and electrical characteristics of aluminum-doped ZnO thin films prepared by sol-gel technique. Journal of Crystal Growth, 192: 430 – 438.

10.    Look, D. C. (2001). Recent advances in ZnO materials and devices. Materials Science and Engineering B, 80(1-3): 383 – 387.

11.    Ravinder, D. (1999). Thermoelectric power studies of zinc substituted copper ferrites. Journal of Alloys and Compounds, 291(1-2): 208 – 214.

12.    Inc.Stat-Ease. (2007). Design Expert Software, Educational Version 7.0.3, Wiley Publishing.

13.    Gonze, X., Amadon, B., Anglade, P. M., Beuken, J. M., Bottin, F. and Boulanger, P. (2009). ABINIT: first-principles approach to material and nanosystem properties. Computer Physical Communication, 180: 2582 – 2615.

14.    Takagi, Y., Ito, M., Majima, K., Nagai, H., and Katsuyama, S. (2002). Thermoelectric properties of (Zn1_yMg_y)1_xAl_xO ceramics prepared by the polymerized complex method. Journal of Applied Physics, 92: 1391 – 1398.

15.    Qu, X., Wang, W., Lv, S., and Jia, D. (2011). Thermoelectric properties and electronic structure of Al-doped ZnO. Solid State Communications, 151(4): 332 –  336.

16.    Han, J., Mantas, P. Q., and Senos, A.M.R. (2001). Effect of Al and Mn doping on the electrical conductivity of ZnO. Journal of the European Ceramic Society, 21(10-11): 1883 – 1886.

17.    Zhang, M., Zhang, C. H. and Shen, J. (2011). First-principles calculation of electronic structure of Mg_xZn1-_xO codoped with aluminium and nitrogen. Chinese Physics B, 20: 017101.

18.    Yang, P., Zhao, Y. and Yang, H. (2015). Investigation on optoelectronic performances of Al, N codoped ZnO: First-principles method. Ceramics International, 41: 2446 – 2452.

19.    Li, P., Deng, S. H., Li, Y. B., Huang, J., Liu, G. H. and Zhang, L. (2011). Aluminum and nitrogen impurities in Wurtzite ZnO: first-principles studies, Physica B, 406: 3125 – 3129.

20.    Ozgur, U., Ya, Liu, C., Teke, A., Reshchikov, M. A., Dogan, S., V., Avrutin, Cho, S. J. and Morkoc, H. (2005). A comprehensive review of ZnO materials and devices. Journal of Applied Physics, 98(4): 1 –103.

21.    Bhan, R. and Dhar, V. (2004). Carrier density approximation for non-parabolic and highly degenerated HgCdTe semiconductors. Semiconductor Science and Technology, 19(3): 413 – 416.

22.    Cheng, H., Xu, X. J., Hng, H. H. and Ma, J. (2009). Characterization of Al-doped ZnO thermoelectric materials prepared by RF plasma powder processing and hot press sintering. Ceramics International, 35(8): 3067 – 3072.