Sains Malaysiana 42(8)(2013):
1139–1144
Microstructural
and Nonlinear Electrical Properties of ZnO Ceramics with
Small Amount of MnO2 Dopant
(Sifat Mikrostruktur dan Elektrik Tak-linear Seramik ZnO dengan Kuantiti Kecil Dopan MnO2)
A.N.
Fauzana, B.Z. Azmi* & M.G.M. Sabri
Department
of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang,
Selangor, D.E. Malaysia
W.R.
Wan Abdullah & M. Hashim
Materials
Synthesis and Characterization Laboratory, Institute of Advanced Technology
Universiti
Putra Malaysia, 43400 UPM Serdang, Selangor D.E. Malaysia
Diserahkan:
27 Jun 2012 /Diterima; 16 Disember 2012
ABSTRACT
A small amount of MnO2 dopant was added to ZnO system to see the
improvement of the ceramic varistor microstructural and nonlinear electrical
properties. The samples were prepared using solid-state method and the
microstructure and nonlinear electrical properties of the ZnO-xMnO2 system
were investigated for × = 0.011 to 0.026 mol%, at three sintering
temperatures, 1180°C, 1240°C and 1300°C for 1 and 2 h sintering time. The XRD and EDAX analysis
showed that the main phase was ZnO while ZnMnO3 and ZnMnO7 as the secondary
phases developed and distributed at the grain boundaries and triple point
junction. The SEM observation revealed that prolonged sintering temperature and
time improved microstructure uniformity and strongly influences the nonlinear
behavior of the samples. The maximum density and grain size have been observed
at 92% of theoretical density and 10.8 μm, respectively and occur at the
highest sintering temperature which is 1300°C. The value of nonlinear
coefficient α is found to increase with the increase of MnO2 doping level up to 0.016
mol% and drop with further doping level increment for all sintering
temperatures and time.
Keywords: MnO2; nonlinear coefficient; ZnO varistor
ABSTRAK
Kuantiti kecil bahan dop MnO2 ditambah kepada sistem
ZnO untuk melihat peningkatan sifat-sifat mikrostruktur dan keelektrikan tak-linear
seramik varistor. Sampel telah disediakan melalui kaedah tindak balas keadaan
pepejal dan ciri-ciri struktur-mikro dan elektrik tak-linear bagi sistem
ZnO-xMnO2 telah
dijalankan untuk kuantiti kecil × = 0.011 sehingga 0.026 mol%, pada tiga
suhu pensinteran, 1180°C, 1240°C dan 1300ºC dengan masa pensinteran 1 dan 2
jam. Analisis XRD dan EDAX menunjukkan bahawa fasa utama adalah ZnO
manakala ZnMnO3 dan ZnMnO7 sebagai fasa kedua
terbentuk dan tertabur di sempadan butiran dan titik simpang tiga. Pemerhatian
melalui SEM menunjukkan bahawa pemanjangan suhu dan masa persinteran
memperbaiki mikrosturktur dan mempengaruhi kelakuan tak-linear sampel.
Ketumpatan dan saiz butiran maksimum telah diperhatikan pada 92% daripada
ketumpatan teori dan 10.8.μm, masing-masing, berlaku pada suhu pensinteran
tertinggi iaitu 1300ºC. Nilai daripada pekali tak-linear α didapati
meningkat dengan peningkatan paras dop MnO2 sehingga tahap
0.016 mol% dan menurun dengan penambahan paras dop seterusnya untuk semua suhu
dan masa pensinteran.
Kata kunci: MnO2;
pekali tak-linear; varistor ZnO
RUJUKAN
Bueno, P.R., Leite, E.R., Oliveira, Orlandi,
M.O. & Longo, E. 2001. Role of oxygen at the grain boundary of metal oxide
varistors: A potential barrier formation mechanism. Applied Physics Letters 29:
48-50.
Filho, F.M., Simoes, A.Z., Ries, A., Perazolli, L., Longo,
E. & Varela, J.A. 2006. Nonlinear electrical behavior of the Cr2O3,
ZnO, CoO and Ta2O5 -doped SnO2 varistors. Ceramics
International 32: 283-289.
Goujon,
C. & Goeuriot, P. 2001. Solid state sintering and high temperature
compression properties of Al-alloy5000/AlN nanocomposites. Materials Science
and Engineering 315: 180-188.
Han,
J., Mantas, P.G. & Senos, A.M.R. 2000. Grain growth in Mn-doped ZnO. Journal
of the European Ceramic Society 20: 2753-2758.
Han,
J., Senos, A.M.R. & Mantas, P.Q. 2002. Varistor behavior of Mn-doped ZnO
ceramics. Journal of the European Ceramic Society 22: 1653-1660.
Hng,
H.H. & Knowles, K.M. 2002. Microstructure and current-voltage characteristics
of praseodymium-doped zinc oxide varistors containing MnO2, Sb2O3 and Co3O4. Journal of Materials Science 37(6):
1143-1154.
Hng,
H.H. & Tse, K.Y. 2008. Effects of MgO doping in ZnO-0.5 mol% V2O5 varistors. Ceramics International 34: 1153-115.
Kelleher,
M.C. & Hashmi, M.S.J. 2008. The effect of vibratory milling on the
powder properties of zinc oxide varistors. Journal of Materials Processing
Technology 201: 645-650.
Lao,
Y.M., Kuo, S.T. & Tuan, W.H. 2009. Influence of ball milling on the
sintering behavior of ZnO powder. Ceramics International 35: 1317-1320.
Leite,
E.R., Varela, J.A. & Longo, E. 1992. A new interpretation for the
degradation phenomenon in ZnO varistors. Journal of Materials Science 27:
5527-5529.
Nahm,
C.W. 2008. Influence of Mn doping on microstructure and DC-accelerated aging
behaviors of ZnO-V2O5-based varistors. Materials Science and Engineering B 150:
32-37.
Onreaboy,
W. & Sirikulrat, N. 2006. Effect of cobalt doping on nonlinearity of zinc
oxide. Materials Science and Engineering B 130: 108-113.
Orlandi,
M.O., Bueno, P.R., Leite, E.R. & Longo, E. 2003. Non- Ohmic behavior of SnO2.
MnO2-based ceramics. Materials Research 6: 279-283.
Riyadi,
S., Muaffif, A.A., Rusydi, A. & Tjia, M.O. 2007. Mn-dopant induced effects
in Zn1-xMnxO compounds. Journal of Physics Condensed Matter 12:
1-8.
Sawalha,
A., Abdeen, M.A. & Sedky, A. 2009. Electrical conductivity study in pure
and doped ZnO ceramic system. Physica B 404: 1316-1320.
Sinha,
A. & Sharma, B.P. 1997. Novel route for preparation of high voltage
varistor powder. Mater. Res. Bull 32:1571-1579.
Subasri,
R., Asha, M., Hembram, K., Rao, G.V.N. & Rao, T.N. 2009. Microwave
sintering of doped nanocryatalline ZnO and characterization for varistor
applications. Materials Chemistry and Physics 115: 677-684.
Wang,
M-H., Yao, C., Zhang, N-F. 2008. Degradation characteristics of low-voltage ZnO
varistor manufactured by chemical co-precipitation processing. Journal of
Materials Processing Technology 202(1/3): 406-411.
Wu,
J., Qi, T., Li, T.T., Qin, Q.W., Li, G.Q., Zhu, B.L., Xiang, Z.D. & Xie,
C.S. 2012. The AC impedance and variable temperature dielectric spectroscopic
analysis of MnO2 doped and un-doped ZnO-V2O5 ceramics. Journal
of Materials Science: Materials in Electronics 23(6): 1143-1150.
*Pengarang
untuk surat-menyurat; email: azmizak@gmail.com
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