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

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.

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

2011 ◽  
Vol 214 ◽  
pp. 168-172 ◽  
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.

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

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.

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

2010 ◽  
Vol 160-162 ◽  
pp. 348-352 ◽  
Author(s):  
Tian Guo Wang ◽  
Qun Qin ◽  
Dong Jian Zhou
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Crystal Lattice ◽  
Breakdown Voltage ◽  
Low Voltage ◽  
Electrical Characteristics ◽  
Electrical Behavior ◽  
Optimal Doping ◽  
Doped Tio2 ◽  
Electrical Permittivity

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.

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.

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

2011 ◽  
Vol 687 ◽  
pp. 34-38 ◽  
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.

scholarly journals An Investigation of the Electrical Behavior of Thermally Sprayed Aluminum Oxide

1996 ◽  
Author(s):  
C.J. Swindeman ◽  
R.D. Seals ◽  
W.P. Murray ◽  
M.H. Cooper ◽  
R.L. White
Keyword(s):  
Electrical Properties ◽  
Aluminum Oxide ◽  
Dielectric Constants ◽  
Electrical Behavior ◽  
X Ray Diffraction ◽  
Heating And Cooling ◽  
Thermally Sprayed Aluminum ◽  
Plasma Sprayed ◽  
And Control ◽  
Steel Substrates

Abstract Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 °C. High purity (>99.5 wt% pure Al2O3) alumina powders were plasma-sprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 °C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the importance of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.

Design, Synthesis, Structural and Textural Characterization, and Electrical Properties of Mesoporous Thin Films Made of Rare Earth Oxide Binaries

2009 ◽  
Vol 21 (11) ◽  
pp. 2184-2192 ◽  
Author(s):  
Jessie Hierso ◽  
Ozlem Sel ◽  
Armelle Ringuede ◽  
Christel Laberty-Robert ◽  
Luc Bianchi ◽  
...  
Keyword(s):  
Thin Films ◽  
Rare Earth ◽  
Electrical Properties ◽  
Rare Earth Oxide ◽  
Design Synthesis ◽  
Textural Characterization ◽  
Mesoporous Thin Films

Thermophysical characterization of oil sands: 3. Electrical properties

1981 ◽  
Vol 18 (4) ◽  
pp. 742-750 ◽  
Author(s):  
M. Das ◽  
R. Thapar ◽  
K. Rajeshwar ◽  
J. DuBow
Keyword(s):  
Electrical Properties ◽  
Oil Sands ◽  
Activation Energies ◽  
Dielectric Constants ◽  
Relaxation Processes ◽  
Electrical Behavior ◽  
Frequency Range ◽  
Oil Sand ◽  
Dipole Relaxation ◽  
Mobile Charges

The electrical behavior of oil sand samples from the Athabasca, N. W. Asphalt Ridge, P. R. Spring, and Circle Cliffs deposits was studied in the frequency range 50 Hz – 103 MHz at ambient temperature and up to 550 °C. Anomalously high dielectric constants (ε′) were measured for these samples at low frequencies (<1 kHz) and at elevated temperatures (>200 °C). Accumulation of mobile charges at the phase boundaries in the oil sand matrix was probably responsible for this effect. These mobile charges were presumably created by thermal fragmentation of oil sand bitumen. The anomalous increase in the low-frequency (50 Hz – 1 MHz) ε′ values at temperatures above 150 °C was also traced to interfacial polarization effects. Dipole relaxation behavior was observed for the various samples at frequencies below ~1 kHz and in the temperature range 150–470 °C. Two distinct relaxation processes were identified. The low-temperature (150–400 °C) process had activation energies for dipole orientation ranging from 4.0 to 9.0 kJ/mol depending on the oil sand specimen. The second relaxation process, which occurred at temperatures above 400 °C, had significantly higher activation energies (30–34 kJ/mol). The occurrence of these dipole relaxation peaks may be relevant in the use of electrical techniques to map the location of pyrolysis zones in in situ oil sand retorts. Measurements on the Athabasca samples in the high-frequency range (1–103 MHz) revealed distinct changes in the dielectric parameters associated with the loss of water from the oil sand matrix. The electrical behavior of oil sands is represented in terms of an equivalent circuit model comprising discrete RC elements corresponding to various components in the oil sand matrix. Such a representation was found to aid in an assignment of the observed changes in the electrical properties with frequency and temperature to distinct physical or chemical processes occurring in the oil sand matrix.

Structure and Dielectric Properties of (Gd0.4Sm0.5Yb0.1)2(Zr1-xCex)2O7 Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 394-397
Author(s):  
Ling Liu ◽  
Qiang Xu ◽  
Fu Chi Wang
Keyword(s):  
Rare Earth ◽  
Dielectric Properties ◽  
Pyrochlore Structure ◽  
Microwave Frequency ◽  
Phase Region ◽  
Dielectric Constants ◽  
Precipitation Method ◽  
Low Dielectric ◽  
Pyrochlore Type ◽  
Co Precipitation

Complex rare-earth zirconates (Gd0.4Sm0.5Yb0.1)2(Zr1-xCex)2O7 (x=0, 0.3, 0.4) powders were synthesized by co-precipitation method. XRD and SEM results revealed that the complex rare-earth zirconates with single pyrochlore structure were prepared and no other phases existed among the grains. The dielectric properties of these compounds were investigated at low and microwave frequencies. It was found that they have intermediate dielectric constants and low dielectric loss in the whole frequency region, and they show the dielectric permittivity with weak frequency dependence. Substituting Zr4+ by Ce4+ leaded to smaller permittivity. Meanwhile, the dielectric contant values increase with increasing in the r(A3+)/r(B4+) value in the pyrochlore-type phase region, which can be explained by the increase in the degree of ordering of oxygen vacancy. This new series of pyrochlore type oxides would be potential candidates for electronic ceramic applications and microwave frequency components.

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