scholarly journals Effects of Ta2O5 on the microstructure and electrical properties of ZnO linear resistance ceramics

2022 ◽  
Author(s):  
Meizhen Zhuo ◽  
Chun-e Huang ◽  
Changzhi Zhao ◽  
Jiongjiong Yin ◽  
Chunying Shen
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Electric Fields ◽  
Crystalline Phase ◽  
Nonlinear Coefficient ◽  
Linear Resistance ◽  
Main Crystalline Phase ◽  
Method Effects ◽  
The Stability ◽  
Grain Boundary Barrier

Abstract ZnO-Al2O3-MgO-TiO2-SiO2-Ta2O5 (ZnO-based) linear resistance ceramics with doping different molar percentages of Ta2O5 were prepared by a conventional ceramics method. Effects of Ta2O5 additives on the phase composition, microstructures, and electrical properties of ZnO-based linear resistive ceramics were investigated. The results show that doping Ta2O5 can refine the grains of the main crystalline phase ZnO and the secondary crystalline phase ZnAl2O4 in terms of microstructure, and also can reduce the grain boundary barrier and optimize the I-V characteristics in terms of electrical properties. In addition, the doping of Ta2O5 can improve the stability of the resistivity , and the impedance frequency indicates that the doping of Ta2O5 makes the sample suitable for high-frequency electric fields. The resistivity of the sample doped with 0.2 mol% Ta2O5 is 56.2 Ω·cm, and this sample has the best grain boundary barrier height, nonlinear coefficient and temperature coefficient of resistance of 0.054 eV, 1.04 and -3.48×10-3 / ℃，respectively.

Effect of Gd2O3 on the Electrical Properties of (Co, Nb)-Doped SnO2 Varistors

2007 ◽  
Vol 280-283 ◽  
pp. 271-274
Author(s):  
Guo Zhong Zang ◽  
Jin Feng Wang ◽  
Hong Cun Chen ◽  
Wen Bin Su ◽  
Chun Ming Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Relative Density ◽  
Nonlinear Coefficient ◽  
Electrical Field ◽  
Barrier Formation ◽  
Sno2 Lattice ◽  
Barrier Model ◽  
Grain Boundary Barrier

The effect of Gd2O3 on the electrical properties of (Co, Nb)-doped SnO2 varistors was investigated. It was found that the nonlinear coefficient presents a peak of α = 30 for the sample doped with 1.5mol% Gd2O3. The increase of the breakdown electrical field from 325V/mm to 1560V/mm with increasing Gd2O3 concentration is mainly attributed to the decrease of the grain size. The decrease of relative density and resistance of grain boundary indicate that Gd2O3 should be a two-sided dopant and the nonlinear coefficient peak was explained. To illustrate the grain-boundary barrier formation of (Gd, Co, Nb) doped SnO2 varistors, a modified defect barrier model was introduced, in which the negatively charged acceptors substituting for Sn ions should not be located at the grain interfaces instead at SnO2 lattice sites of depletion layers.

Electrical Characterization of the Grain-Boundary Region of SnO2 Varistors

2006 ◽  
Vol 518 ◽  
pp. 235-240 ◽  
Author(s):  
M. Žunić ◽  
Z. Branković ◽  
G. Branković ◽  
D. Poleti
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Electric Fields ◽  
Electrical Characterization ◽  
Boundary Region ◽  
Current Voltage ◽  
Schottky Type ◽  
Boundary Properties ◽  
Current Voltage Characteristics

The effect of Co, Cr and Nb on the electrical properties of the grain boundaries of SnO2-based varistors was investigated. The powders were prepared by the method of evaporation and decomposition of solutions and suspensions. Varistor samples were obtained by uniaxial pressing followed by sintering at 1300 °C for 1h. The electrical properties of the grain-boundary region, such as resistance (R) and capacitance (C), were determined using ac impedance spectroscopy in the 27-330 °C temperature interval. Activation energies for conduction (EA) were calculated from the Arrhenius equation. The non-linear coefficients (α) and the breakdown electric fields (Eb) of the samples were determined from the current-voltage characteristics. The potential barrier height (Φb) was calculated using the Schottky-type conducting model. After a comparison of the characteristic parameters for different varistor compositions it was found that the Cr/Nb ratio has a crucial influence on the grain-boundary properties in SnO2 varistors.

Influence of Al2O3 Doping on the Microstructure and Current–Voltage Characteristics of ZnO-Based Linear Resistance Ceramics

2011 ◽  
Vol 480-481 ◽  
pp. 556-559
Author(s):  
Jian Feng Zhu ◽  
Yong Zhou ◽  
Hai Bo Yang ◽  
Fen Wang
Keyword(s):  
Electrical Properties ◽  
Temperature Coefficient ◽  
Raw Materials ◽  
Nonlinear Coefficient ◽  
Al2o3 Content ◽  
Linear Resistance ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Resistance Temperature Coefficient ◽  
Al2o3 Doping

ZnO-based linear resistance ceramics were synthesized using Al2O3 doped ZnO-based system as raw materials by sintered at 1340 °C for 3 h. The effects of Al2O3 content ranged from 1 to 15 wt% on the microstructure and electrical properties of the ceramics were investigated in detail. The results show that the electrical properties such as nonlinear coefficient, resistivity and resistance temperature coefficient have been obviously influenced by Al2O3 doping. The optimal samples obtained by doping Al2O3 with 9 wt% have a nonlinear coefficient of 1.3, resistivity of 130 (Ω•cm) and resistance temperature coefficient of -5.4×10-3/ °C.

Effect of La2O3 on the Microstructure and Electrical Properties of (Ti,Sn)O2 Varistor Ceramics

2010 ◽  
Vol 152-153 ◽  
pp. 1391-1394
Author(s):  
Mao Hua Wang ◽  
Gang Li ◽  
Chao Yao
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Experimental Evidence ◽  
Low Voltage ◽  
Nonlinear Coefficient ◽  
Electrical Characteristics ◽  
Electrical Behavior ◽  
Optimal Doping ◽  
Nonlinear Properties ◽  
Ceramic Sintering

(Ti,Sn)O2 varistors doped with different amount of La2O3 were obtained by ceramic sintering processing at 1250 . The effect of La2O3 on the microstructure and nonlinear electrical behavior of the (Ti,Sn)O2 ceramics were investigated. The ceramics have nonlinear coefficients of α=6.2–8.5. Experimental evidence shows that small quantities of La2O3 improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 1.0mol% La2O3 leads to a low breakdown voltage of 18.1V/mm, a high nonlinear coefficient of 8.5, which is consistent with the highest and narrowest grain boundary barriers of the ceramics.In view of these electrical characteristics, the (Ti,Sn)O2 varistors with 1.0mol% La2O3 ceramic is a viable candidate for low voltage varistor devices. The characteristics of the ceramics can be explained by the effect of the substitution of La3+ for Ti4+ or Sn4+.

Effect of Calcination of the Raw Materials on the Microstructure and Electrical Properties of ZnO-Based Linear Resistance Ceramics

2012 ◽  
Vol 724 ◽  
pp. 327-330
Author(s):  
Jian Feng Zhu ◽  
Yong Zhou
Keyword(s):  
Electrical Properties ◽  
Temperature Coefficient ◽  
Raw Materials ◽  
Nonlinear Coefficient ◽  
Ceramic Method ◽  
Linear Resistance ◽  
Resistance Temperature Coefficient

ZnO-based linear resistance ceramics were fabricated by the conventional ceramic method. The effect of calcination of the raw materials on the microstructure and electrical properties was investigated in detail. The results show that the electrical properties, such as resistivity, nonlinear coefficient and resistance temperature coefficient, have been obviously influenced by the calcining process. The optimal samples fabricated with the materials calcinated for twice possess the highest stabilization of resistivity. Meanwhile, the resistance temperature coefficient is improved by 30%, and the nonlinear coefficient of voltage decreases to 1.16, decreased by 20.7%.

Influence of Sintering Temperature on the Electrical Properties of (La, Ta)-Doped TiO2 Capacitor-Varistor Ceramics

2011 ◽  
Vol 197-198 ◽  
pp. 294-297 ◽  
Author(s):  
Qun Qin ◽  
Tian Guo Wang ◽  
Wen Jun Zhang
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Breakdown Voltage ◽  
Barrier Layer ◽  
Low Voltage ◽  
Sintering Temperature ◽  
Nonlinear Coefficient ◽  
Nonlinear Properties

An investigation was made of low voltage TiO2 varistors doped with Ta2O5 and La2O3. TiO2 ceramics doped with 0.7 mol% La2O3 and 0.1 mol% Ta2O5 were sintered at different temperature ranging from 1350 to 1450°С . The influence of sintering temperature on microstructure and nonlinear properties of the (La, Ta)-doped TiO2 ceramics was studied. The varistor of 99.2 mol%-0.7 mol%La2O3-0.1 mol% Ta2O5 composite sintered at 1380°С has a maximal nonlinear coefficient of α =5.2 and a low breakdown voltage of 7.6 V/mm, which is consistent with its highest grain-boundary barriers. According to these results, it is suggested that the sample sintered at 1380°С forms the most efficient boundary barrier layer. Therefore, the sintering temperature is a very important varible which should not be despised in the project of TiO2 based varistors production.

Effect of Er2O3 on the Microstructure and Electrical Properties of (Er, Ta)-Doped Tio2 Capacitor-Varistor Ceramics

2011 ◽  
Vol 216 ◽  
pp. 563-567
Author(s):  
Tian Guo Wang ◽  
Qun Qin ◽  
Dong Jian Zhou
Keyword(s):  
Grain Size ◽  
Rare Earth ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Breakdown Voltage ◽  
Nonlinear Coefficient ◽  
Rare Earth Oxide ◽  
Second Phase ◽  
Barrier Model

TiO2-based capacitor-varistor ceramics doped with Er2O3 were prepared and the microstructures and nonlinear electrical properties were investigated. The results show that there exist second phase Er2TiO3 on the surface of TiO2 grains. The grain size was found to decrease with increasing Er2O3 content. The addition of rare earth oxide Er2O3 leads to increase the nonlinear coefficient and the breakdown voltage. It was found that the nonlinear coefficient presents a peak of α = 4.5 for the sample doped with 1.1 mol% Er2O3, which isconsistent with the highest grain boundary in the composition. In order to illustrate the role of grain boundary barriers for TiO2-Ta2O5-Er2O3 varistors, a grian boundary defect barrier model was introduced.

Effects of Y2O3 and In2O3 on the Electrical Properties of SnO2-Based Varistors

2012 ◽  
Vol 217-219 ◽  
pp. 741-745
Author(s):  
Guo Zhong Zang ◽  
Li Ben Li ◽  
Sheng Lai Wang
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Barrier Height ◽  
Energy Levels ◽  
Nonlinear Coefficient ◽  
Electrical Behavior ◽  
Electrical Field

The effects of Y2O3 and In2O3 on the microstructure and electrical properties of SnO2-based varistors were investigated. It was observed that the grain size of the samples decreased with doping Y2O3 and In2O3 and accordingly, the breakdown electrical field EB increased greatly. The measurements of barrier height and grain size reveal that the variation of grain size was not the only reason for the change of electrical properties of the sample doped with In2O3 and, the improvement of nonlinear coefficient α may mainly attribute to the increase of barrier height. Some energy levels of different state defects on the grain boundary were obtained and the energy about 0.15 eV detected here of all the samples may be attributed to the activation of . The different effects of doping Y2O3 and In2O3 indicate that In2O3 is more effective to improve nonlinear electrical behavior and breakdown electrical field of SnO2-based varistors.

Grain boundary structure of A ZnO-Bi2O3-CoO varistor

1990 ◽  
Vol 48 (4) ◽  
pp. 374-375
Author(s):  
Yoko Suyama ◽  
Yoshitsugu Tomokiyo ◽  
Kunihiro Terasaka
Keyword(s):  
High Resolution ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Nonlinear Coefficient ◽  
Analytical Electron Microscopy ◽  
Ceramic Technology ◽  
Boundary Structure ◽  
Oxide Ceramic ◽  
Zno Varistor ◽  
20 Nm

The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary structures. The microstructures of ulticomponent varistors are very complicated and quite sensitive to concentration and thermal history. It is not clear which microstructures play an important role for the electrical properties such as nonlinear coefficient and varistor voltage, and for the degradiation. In the present paper the microstructure of ZnO varistor was investigated by means of analytical electron microscopy to elucidate the relation between the microstructures and the electrical properties. In order to obtain local information on the microstructures of grain boundary and multiple junction, we combined the various TEM techniques such as high-resolution imaging (HREM), microprobe diffraction (μ ED), convergent-beam electron diffraction (CBED) and energy dispersive x-ray spectroscopy (EDX).ZnO varistor samples with addition of 0.5molZ% Bi2O3 + 0∼0.5molZ% CoO were prepared by conventional mixed-oxide ceramic technology. The thin foils prepared from the samples sintered at 800, 900 and 1000 °C were examined either by an analytical TEM, JEM-2000FX at 200 kV or a high resolution TEM, JEM-4000EX at 400 kV. The diameters of electron probe were less than 10 nm for μ ED and about 20 nm for EDX and 10∼20 nm for CBED.

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