Microstructure and Electrical Properties of Nd2O3-Doped TiO2-Ta2O5-Based Capacitor-Varistor Ceramics

A low-voltage TiO2 capacitor-varistor ceramics doped with Ta2O5 and Nd2O3 was systematically researched. The effect of Nd2O3 on the microstructure, nonlinear electrical properties, and dielectric properties of TiO2-based ceramics was investigated. It was found that an optimal doping composition of 99.20 mol% TiO2-0.10 mol%Ta2O5-0.7 mol% Nd2O3 was obtained with low breakdown voltage of 8.5 v/mm, high nonlinear constant of 4.0, ultrahigh electrical permittivity of 1.07× 105 and low tanδ of 0.39. In view of these electrical characteristics, the ceramics of 99.20 mol% TiO2-0.10 mol%Ta2O5-0.7 mol% Nd2O3 is a viable candidate for capacitor-varistor functional devices. The theory of defects in the crystal lattice was introduced to explain the nonlinear electrical behavior of the Nd2O3-doped TiO2-based varistor ceramics.

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Effect of Temperature on Microstructure and Electrical Properties of (Y, Ta)-Doped TiO2 Capacitor-Varistor Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.214.173 ◽

2011 ◽

Vol 214 ◽

pp. 173-177

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Wen Jun Zhang

Keyword(s):

Dielectric Properties ◽

Electrical Properties ◽

Breakdown Voltage ◽

Sintering Temperature ◽

Nonlinear Coefficient ◽

Effect Of Temperature ◽

Electrical Characteristics ◽

Electrical Behavior ◽

Nonlinear Properties ◽

Electrical Permittivity

The microstructure and nonlinear electrical behavior and dielectric properties of the varistor, which are composed of (Y2O3, Ta2O5)-doped TiO2 ceramics, were investigated for various sintering temperatures. It is assumed that the moderate sintering temperature improves the permitivity of TiO2 ceramics, together with high nonlinear properties. The varistor of 99.6 mol%-0.3 mol%Y2O3-0.1 nol%Ta2O5 composite sintered at 1400 °C has a maximal nonlinear coefficient of α =4.4, a low breakdown voltage of 10.8 V/mm, the ultrahigh electrical permittivity of 7.73× 104 and low tanδ of 0.34. The sintering temperature plays an important an important role on the nonlinear electrical characteristics and dielectric properties of the ceramics through its influences on the microstructure of samples.

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Effect of La2O3 on the Electrical Properties of WO3-Based Varistor Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.480-481.137 ◽

2011 ◽

Vol 480-481 ◽

pp. 137-141

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Wen Jun Zhang

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Electrical Properties ◽

Crystal Lattice ◽

Breakdown Voltage ◽

High Dielectric Constant ◽

Electrical Characteristics ◽

Electrical Behavior ◽

High Dielectric

The nonlinear electrical behavior and dielectric properties of WO3-based ceramics with various La2O3 contents have been investigated. Breakdown voltages Eb of WO3 doped with La2O3 are lower than that of undoped WO3, indicating that the dopant can reduce the breakdown voltage. The dielectric constant of doped samples is higher than that of undoped samples, and the high dielectric constant makes them suitable as capacitor-varistor materials. The theory defects in the crystal lattice was introduced to explain the nonlinear electricial behavior of the La2O3-doped WO3 ceramics. In view of these electrical characteristics, the WO3 ceramic doped with La2O3 is a viable candidate for capacitor-varistor functional devices.

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Effect of CeO2 on the Electrical Properties of Ta2O5-Doped TiO2 Capacitor-Varistor Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.214.168 ◽

2011 ◽

Vol 214 ◽

pp. 168-172 ◽

Cited By ~ 4

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Wen Jun Zhang

Keyword(s):

Dielectric Properties ◽

Electrical Properties ◽

Grain Boundary ◽

Dielectric Constants ◽

Electrical Behavior ◽

Optimal Doping ◽

Doped Tio2 ◽

Nonlinear Properties ◽

Ceramic Sintering ◽

Electrical Permittivity

TiO2 varistors doped with 0.1 mol% Ta and different concentrations of CeO2 were obtained by ceramic sintering processing at 1400 °C. The effect of CeO2 on the nonlinear electrical behavior and dielectric properties of the Ta2O5-doped TiO2 ceramics were investigated. The nonlinear current (I)-voltage (V) characteristics of TiO2 are examined when doped with small quantities (0.1-0.9 mol%) of CeO2. It is found that CeO2 affects the electrical properties and the dielectric properties of the TiO2-based varistors. The samples have the nonlinear coefficients (α) values of (3.0-5.0), breakdown voltages (10-30 V/mm) and ultrahigh dielectric constants which is up to 105. A small quantities of CeO2 can improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 99.4 mol% TiO2 - 0.1 mol% Ta2O5 - 0.30 mol% CeO2 was obtained with low breakdown voltage of 14.2 V/mm, high nonlinear constant of 4.5 , an ultrahigh electrical permittivity of 8.381.22×105 (measured at 1 kHz) and low tanδ of 0.32, which is consistent with the highest grain boundary barriers of the ceramics. The theory of defects in the crystal lattice was introduced to explain the nonlinear electrical behavior of the CeO2-doped TiO2-based varistor ceramics.

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Effect of Pr on the Microstructure and Electrical Properties of Ta-Doped TiO2 Capacitor-Varistor Ceramics

Materials Science Forum ◽

10.4028/www.scientific.net/msf.687.34 ◽

2011 ◽

Vol 687 ◽

pp. 34-38 ◽

Cited By ~ 1

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Dong Jian Zhou

Keyword(s):

Grain Size ◽

Dielectric Properties ◽

Electrical Properties ◽

Impedance Spectroscopy ◽

Electrical Characteristics ◽

Electrical Behavior ◽

Optimal Doping ◽

Nonlinear Properties ◽

Ceramic Sintering ◽

Electrical Permittivity

TiO2 varistors doped with 0.1 mol% Ta and different concentrations of Pr3+ were obtained by ceramic sintering processing at 1400 °C and their properties were characterized by XRD, SEM, I-V and impedance spectroscopy. The effect of Pr on the microstructure, nonlinear electrical behavior and dielectric properties of the Ta-doped TiO2 ceramics were investigated. It is found that Pr affects the grain size, electrical properties and the dielectric properties of the TiO2-based varistors. The samples have the nonlinear coefficients (α) values of (3.0-5.0) with low breakdown voltages (4-30 V/mm). A small quantities of Pr can improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 0.5 mol% Pr3+ leads to a low breakdown voltage of 9.2 V/mm, a high nonlinear constant of 4.9 and an ultrahigh electrical permittivity of 8.38×104 (at 1 kHz), which is consistent with the highest grain boundary barriers of the ceramics. In view of these electrical characteristics, the TiO2-0.5 mol% Pr3+ceramic is a viable candidate for capacitor-varistor functional devices. The defects theory was introduced to explain the nonlinear electrical behavior of Pr-doped TiO2 ceramics.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.152-153.1391 ◽

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+.

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Effect of Sm2O3 on the Electrical Properties of TiO2-Ta2O5-Based Capacitor-Varistor Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.213.246 ◽

2011 ◽

Vol 213 ◽

pp. 246-249

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Dong Jian Zhou

Keyword(s):

Rare Earth ◽

Dielectric Properties ◽

Electrical Properties ◽

Rare Earth Oxide ◽

Dielectric Constants ◽

Second Phase ◽

Electrical Behavior ◽

Effective Boundary ◽

Electrical Permittivity ◽

Change Of Microstructure

TiO2 ceramics doped with 0.1 mol% Ta2O5 and different concentrations of rare earth oxide Sm2O3 were obtained by sintering at 1450 °C. As a varisor material, the microstructure, the nonlinear electrical behavior and dielectric properties of these ceramics were investigated. SEM and XRD were carried out to study the change of microstructure. The results show that there exist second phase (Sm2Ti2O3) on the surface on the surface of TiO2 grains. The ceramics have nonlinear coefficients of α = 2.0-4.0 and ultrahigh relative dielectric constants which is up to 104. The sample doped with 0.5 mol% Sm2O3 exhibits high nonlinear constant of 3.7, low breakdown voltage of 21.5 v/mm, ultrahigh electrical permittivity of 4.25× 104 and low tanδ of 0.37. It is suggested that the sample doped with 0.5 mol% Sm2O3 forms the most effective boundary barrier layer. The defects theory was introduced to illustrate the nonlinear electrical behavior of TiO2-Ta2O5-Sm2O3 varistor ceramics.

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Microstructure and Electrical Properties of Y2O3-Doped WO3-Based Varistor Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.233-235.2499 ◽

2011 ◽

Vol 233-235 ◽

pp. 2499-2502

Author(s):

Tian Guo Wang ◽

Qun Qin ◽

Wen Jun Zhang

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Electrical Properties ◽

Breakdown Voltage ◽

High Dielectric Constant ◽

Low Voltage ◽

Nonlinear Coefficient ◽

High Dielectric

WO3-based varistors doped with Y2O3 were prepared and the microstructure, nonlinear electrical properties, and dielectric properties were investigated. Breakdown voltages Eb of WO3 doped with Y2O3 are lower than that of undoped WO3, indicating that the dopant can reduce the breakdown voltage. The dielectric constant of doped samples is higher than that of undoped samples, and the high dielectric constant makes them suitable as capacitor-varistor materials. It was found that the sample of WO3-0.5 mol% Y2O3 sintered at 1150 °C has an optimal nonlinear coefficient of 3.4 and a breakdown voltage of 17.1 V/mm. WO3 ceramic doped with Y2O3 is a new kind of low voltage capacitor-varistor material.

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