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 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.

Effect of WO3 Doping on Microstructural and Electrical Properties of ZnO-Pr6O11 Based Varistor Materials

2013 ◽  
Vol 591 ◽  
pp. 54-60
Author(s):  
Xiu Li Fu ◽  
Yan Xu Zang ◽  
Zhi Jian Peng
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Grain Growth ◽  
Doping Level ◽  
Nonlinear Coefficient ◽  
Current Voltage ◽  
Average Grain Size ◽  
Current Voltage Characteristics ◽  
Voltage Performance

The effect of WO3doping on microstructural and electrical properties of ZnO-Pr6O11based varistor materials was investigated. The doped WO3plays a role of inhibitor in ZnO grain growth, resulting in decreased average grain size from 2.68 to 1.68 μm with increasing doping level of WO3from 0 to 0.5 mol%. When the doping level of WO3was lower than 0.05 mol%, the nonlinear current-voltage characteristics of the obtained varistors could be improved significantly with increasing amount of WO3doped. But when the doping level of WO3became higher, their nonlinear current-voltage performance would be dramatically deteriorated when more WO3was doped. The optimum nonlinear coefficient, varistor voltage, and leakage current of the samples were about 13.71, 710 V/mm and 13 μA/cm2, respectively, when the doping level of WO3was in the range from 0.03 to 0.05 mol%.

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.

The Role of Crystallization of an Intergranular Glassy Phase in Determining Grain Boundary Residual Stresses in Debased Aluminas

1989 ◽  
Vol 170 ◽  
Author(s):  
Nitin P. Padture ◽  
Helen M. Chan ◽  
Brian R. Lawn ◽  
Michael J. Readey
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Residual Stresses ◽  
Glassy Phase ◽  
Analytical Techniques ◽  
Ceramic Materials ◽  
Strength Test ◽  
Second Phase

AbstractThe influence of microstructure on the crack resistance (R-curve) behavior of a commercial debased alumina containing large amounts of glassy phase (28 vol %) has been studied using the Indentation-Strength test. The effect of two microstructural variables, viz. grain size and the nature of the intergranular second phase (glassy or crystalline) has been evaluated. Crystallization of the intergranular glass was carried out in order to generate residual stresses at the grain boundaries, which have been shown to enhance R-curve behavior in ceramic materials. Enhancement of the R-curve behavior was observed with the increase in grain size. However, no effect of the nature of the intergranular second phase on the R-curve behavior, in small and large grain materials, was observed. The results from characterization of these materials using various analytical techniques is presented, together with possible explanations for the observed effects.

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.

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.

scholarly journals Effect of Rare Earth Ce on Deep Stamping Properties of High-Strength Interstitial-Free Steel Containing Phosphorus

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1473
Author(s):  
Hao Wang ◽  
Yanping Bao ◽  
Chengyi Duan ◽  
Lu Lu ◽  
Yan Liu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Rare Earth ◽  
High Strength ◽  
Rolling Process ◽  
P Element ◽  
Second Phase ◽  
Strengthening Effect ◽  
Interstitial Free ◽  
If Steel

The influence of rare earth Ce on the deep stamping property of high-strength interstitial-free (IF) steel containing phosphorus was analyzed. After adding 120 kg ferrocerium alloy (Ce content is 10%) in the steel, the inclusion statistics and the two-dimensional morphology of the samples in the direction of 1/4 thickness of slab and each rolling process were observed and compared by scanning electron microscope (SEM). After the samples in each rolling process were treated by acid leaching, the three-dimensional morphology and components of the second phase precipitates were observed by SEM and energy dispersive spectrometer (EDS). The microstructure of the sample was observed by optical microscope, and the grain size was compared. Meanwhile, the content and strength of the favorable texture were analyzed by X-ray diffraction (XRD). Finally, the mechanical properties of the product were analyzed. The results showed that: (1) The combination of rare earth Ce with activity O and S in steel had lower Gibbs free energy, and it was easy to generate CeAlO3, Ce2O2S, and Ce2O3. The inclusions size was obviously reduced, but the number of inclusions was increased after adding rare earth. The morphology of inclusions changed from chain and strip to spherical. The size of rare earth inclusions was mostly about 2–5 μm, distributed and dispersed, and their elastic modulus was close to that of steel matrix, which was conducive to improving the structure continuity of steel. (2) The rare earth compound had a high melting point. As a heterogeneous nucleation point, the nucleation rate was increased and the solidification structure was refined. The grade of grain size of products was increased by 1.5 grades, which is helpful to improve the strength and plasticity of metal. (3) Rare earth Ce can inhibit the segregation of P element at the grain boundary and the precipitation of Fe(Nb+Ti)P phase. It can effectively increase the solid solution amount of P element in steel, improve the solid solution strengthening effect of P element in high-strength IF steel, and obtain a large proportion of {111} favorable texture, which is conducive to improving the stamping formability index r90 value.

scholarly journals Structural and Electrical Studies on ZnO-Based Thin Films by Laser Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Shanyue Zhao ◽  
Yinqun Hua ◽  
Ruifang Chen ◽  
Jian Zhang ◽  
Ping Ji
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Laser Irradiation ◽  
Nonlinear Coefficient ◽  
Acceptor State ◽  
Xrd Pattern ◽  
Electrical Studies ◽  
Structural And Electrical Properties

The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD pattern shows that the thin films were highly textured along thec-axis and perpendicular to the surface of the substrate. Raman spectra reveal that Bi2O3segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the film was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary were interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the breakdown voltage reduced to 5.34 V.

Microstructure and Electrical Properties of ZnO-Pr6O11-Dy2O3-Based Varistor Ceramics Doped with La2O3

2007 ◽  
Vol 336-338 ◽  
pp. 680-683
Author(s):  
Jing Nan Cai ◽  
Yuan Hua Lin ◽  
Rong Juan Zhao ◽  
Ce Wen Nan ◽  
Jin Liang He
Keyword(s):  
Rare Earth ◽  
Phase Composition ◽  
Electrical Properties ◽  
Rare Earth Elements ◽  
Leakage Current ◽  
Breakdown Voltage ◽  
Intergranular Phase ◽  
Ceramic Method ◽  
Sem Micrographs ◽  
Ceramic Samples

ZnO-Pr6O11-Dy2O3-based varistor ceramics doped with 0~1.5 mol% La2O3 were fabricated by a conventional ceramic method. All the samples were sintered at 1350 oCfor 2 h. The phase composition and microstructure of the ceramic samples have been investigated by XRD, SEM and EDS. The results of SEM micrographs indicated that the La2O3 additives can promote ZnO grain’s growth, and the rare earth elements dispersed mainly in the intergranular phase observed by EDS. The electrical properties of the samples determined by the V-I curves revealed that the breakdown voltage of samples decreases from 508 V/mm to about 100 V/mm with the increase of La2O3, and the nonlinear exponent also decreases from 20.2 to 13.2. The typical leakage current is about 10.2 μA for the sample doped with 0.5 mol% La2O3.

Effect of rare-earth species on the wear properties of α sialon and β silicon nitride ceramics under tribochemical type conditions

2004 ◽  
Vol 19 (9) ◽  
pp. 2750-2758 ◽  
Author(s):  
Mark I. Jones ◽  
Kiyoshi Hirao ◽  
Hideki Hyuga ◽  
Yukihiko Yamauchi
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Wear Behavior ◽  
Rare Earth Oxide ◽  
Lower Amount ◽  
Boundary Phase ◽  
Wear Properties ◽  
Sintering Additives ◽  
Nitride Ceramics ◽  
Worn Surfaces

The wear properties under low loads of β Si3N4 and α sialon materials sintered with different rare-earth oxide sintering additives have been studied under dry sliding conditions using block-on-ring wear tests. All the worn surfaces showed an absence of fracture and smooth surfaces with the presence of an oxygen-rich filmlike debris indicating tribochemically induced oxidation of the surfaces. Extensive grain boundary removal was observed on the worn surfaces thought to be due to adhesion between this silicate phase and the tribochemically oxidized surfaces. The resistance to such oxidation and the properties of the residual grain boundary phase are thought to be important parameters affecting the wear behavior under the present testing conditions. For both the β Si3N4 and α sialon materials, there was an increase in wear resistance with decreasing cationic radius of the rare earth, thought to be due to improved oxidation resistance, and this was more remarkable in the case of the sialon materials where the incorporation of the sintering additives into the Si3N4 structure results in a lower amount of residual boundary phase.

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