Effect of Al Addition on Electrical Properties of ZnO-based Varistor Ceramics

doi:10.15541/jim20160080

Abstract

Abstract:

The influences of trace ionic Al addition on the microstructure, electrical properties and intrinsic defects concentration of ZnO-based varistor ceramics were investigated. The results show that the peak value of imaginary permittivity can be used to represent intrinsic defect concentration. Trace ionic Al addition greatly reduces the intrinsic defect concentrations, i.e. the peak value of imaginary permittivity, representing the oxygen vacancy defect decreases from 88.8 to 1.7, and the corresponding zinc interstitial defect decreasing from 133.4 to 8.1. With the increase of ionic Al addition, the varistor voltage increases from 235 V/mm to 292 V/mm and the average grain size decreases from 9.15 μm to 6.24 μm. The results indicate that Al addition effectively restrains the formation of intrinsic defects in ZnO-based varistor ceramics, leading to the change of microstructure and electrical properties. Furthermore, the inhibition mechanism of Al addition to the intrinsic defects in ZnO-based varistor ceramics is discussed, and the relationships between microstructure, electrical properties, dielectric properties and intrinsic defects are established.

Key words: ZnO-based varistor ceramic, Al dopant, intrinsic defect

CLC Number:

TM28

LIN Jia-Jun, LI Sheng-Tao, HE Jin-Qiang, LIU Wen-Feng. Effect of Al Addition on Electrical Properties of ZnO-based Varistor Ceramics[J]. Journal of Inorganic Materials, 2016, 31(9): 981-986.

Figures/Tables 8

Fig. 1 XRD patterns of ZnO varistor ceramic samples doped with various Al amounts

Table 1 Lattice constant of ZnO grain in ZnO varistor ceramic samples doped with various Al amounts

Al amount/mol%	a /nm	c /nm
0	0.323947	0.518892
0.006	0.324105	0.519197
0.015	0.324071	0.519127
0.030	0.324173	0.519337

Fig. 2 SEM images of ZnO varistor ceramic samples doped with various Al amounts

Fig. 3 I-V characteristics of ZnO varistor ceramic samples doped with various Al amounts

Table 2 Nonlinear coefficient and varistor voltage of ZnO varistor ceramic samples doped with various Al amounts

Sample	α	E /(V·mm^-1)
Al-0	41.98	235
Al-60	37.98	249
Al-150	20.56	272
Al-300	14.26	292

Fig. 4 Dielectric spectra of ZnO varistor ceramic samples doped with various Al amounts at room temperature (25℃)

Fig. 5 Dielectric spectrum of ZnO varistor ceramic samples doped with various Al amounts at low temperature (-120℃~-60℃)

Fig. 6 (a) Dielectric spectra of ZnO varistor ceramic samples doped with various Al amounts at -100℃ and (b) peak value of relaxation peak for samples doped with various Al amounts

References 20

[1]	EDA K.Zinc oxide varistor.IEEE Electrical Insulation Magazine, 1989, 5(6): 2872-2882.
[2]	GUPTA T K.Application of zinc oxide varistor.Journal of the American Ceramic Society, 1990, 73(7): 1817-1840.
[3]	LIU S Q, HUANG K L, SHONG Z F, et al.Preparation of rare earth oxide doped ZnO varistor and its electrical properties.Journal of Inorganic Materials, 2000, 15(2): 376-380.
[4]	LI J Y, LI S T, CHENG P F, et al.Advances in ZnO-Bi2O3 based varistors.Journal of Materials Science: Materials in Electronics, 2015, 26(7): 4782-4809.
[5]	LI S T, LI J Y, LIU W F, et al.Advances in ZnO varistors in China during the past 30 years-fundamentals, processing, and applications.IEEE Electrical Insulation Magazine, 2015, 31(4): 35-44.
[6]	WU J Z, GUO Y Y.Influences of additives on properties of nonlinear ZnO ceramics.Journal of Inorganic Materials, 1991, 6(2): 185-191.
[7]	CLARKE D R.Varistor ceramics.Journal of the American Ceramic Society, 1999, 82(3): 485-502.
[8]	BERNIK S, DANEU N.Characteristics of ZnO-based varistor ceramics doped with Al2O3.Journal of the European Ceramic Society, 2007, 27(10): 3163-3170.
[9]	HAN J P, MANTAS P Q, SENOS A M R. Effect of Al and Mn doping on the electrical conductivity of ZnO.Journal of the European Ceramic Society, 2001, 21(10/11): 1883-1886.
[10]	WANG M H, HU K A, ZHAO B Y, et al.Electrical characteristics and stability of low voltage ZnO varistors doped with Al.Materials Chemistry and Physics, 2006, 100(1): 142-146.
[11]	SEDKY A, SAWALHA A A, YASSIN A M.Enhancement of electrical conductivity by Al-doped ZnO ceramic varistors.Physica B, 2009, 404(20): 3519-3524.
[12]	CHENG L H, ZHENG L Y, MENG L, et al.Electrical properties of Al2O3-doped ZnO varistors prepared by Sol-Gel process for device miniaturization.Ceramics International, 2012, 38(1): 457-461.
[13]	WANG Y, LUO F, ZHANG L, et al.Microwave dielectric properties of Al-doped ZnO powders synthesized by coprecipitation method.Ceramics International, 2013, 39(8): 8723-8727.
[14]	ZAMIRI R, SINGH B, SCOTT M B, et al.Structural and dielectric properties of Al-doped ZnO nanostructures.Ceramics International, 2014, 40(4): 6031-6036.
[15]	ALIM M A.Admittance-frequency response in zinc-oxide varistor ceramics.Journal of the American Ceramic Society, 1989, 72(1): 28-32.
[16]	LI S T, CHENG P F, LI J Y, et al.Investigation on defect structure in ZnO varistor ceramics by dielectric spectra.International Conference on Solid Dielectrics, 2007: 207-210.
[17]	CHENG P F, LI S T, ZHANG L, et al. Characterization of intrinsic donor defects in ZnO ceramics by dielectric spectroscopy. Applied Physics Letters, 2008, 93(1): 012902-1-3.
[18]	ZHAO X T, LI J Y, LI H, et al. Intrinsic and extrinsic defect relaxation behavior of ZnO ceramics. Journal of Applied Physics, 2012,111(12): 124106-1-8.
[19]	WANG C C, LIU L N, LI Q J, et al. Revisiting the low-temperature dielectric properties of ZnO. Journal of Applied Physics, 2014, 116(12): 124101-1-8.
[20]	ZHAO X T, LIAO R J, LIANG N C, et al. Role of defects in determining the electrical properties of ZnO ceramics. Journal of Applied Physics, 2014, 116(1): 014103-1-10.