Synthesis of Pr6O11 Doped Zinc Varistors by High-Energy Milling

2010 ◽  
Vol 105-106 ◽  
pp. 314-316
Author(s):  
Guo Quan Qi ◽  
Jian Feng Zhu ◽  
Hai Bo Mao ◽  
Yang Wu ◽  
Hai Bo Yang ◽  
...  
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Milling Time ◽  
Sintering Temperature ◽  
Raw Materials ◽  
High Energy ◽  
Linear Coefficient ◽  
High Energy Milling ◽  
Zno Varistors ◽  
Doped Zno

High voltage zinc varistors was synthesized by high energy milling with Pr6O11 doped ZnO-Bi2O3 system as raw materials. The effects of milling time and sintering temperature on the electrical properties were investigated. The results show that high-energy milling decreases the sintering temperature of the ZnO varistors. The material derived from high-energy milling exhibit high density and good electrical properties at the sintering temperature from 1080 to 1180°C. The samples sintered at 1100 °C have average crystalline grain size of about 5 µm with the optimum values of electrical properties, gradient voltage V1mA is 371 V/mm, leakage current IL is 0.62 µA, non linear coefficient α is 60.

Synthesis of Pr6O11 Doped ZnO-Based Varistors by Pyrogenic Decomposition of Nitrate

2011 ◽  
Vol 675-677 ◽  
pp. 179-182
Author(s):  
Jian Feng Zhu ◽  
Guo Quan Qi ◽  
Hai Bo Mao ◽  
Hai Bo Yang ◽  
Fen Wang
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Leakage Current ◽  
Sintering Temperature ◽  
Linear Coefficient ◽  
Average Grain Size ◽  
Non Linear ◽  
Different Temperatures ◽  
Zno Powders ◽  
Doped Zno

Pr6O11 doped ZnO-based varistor powders were prepared by a method of pyrogenic decomposition nitrate, which were together with ZnO powders, made into rounded mass and sintered at different temperatures. The effects of sintering temperatures on the composition, microstructure and electrical properties of Pr6O11 doped ZnO-based varistors were investigated. The results show that the optimum sintering temperature is at 1150 °C with 6 μm ZnO average grain size and the samples possess the advantageous electrical properties: varistor voltage of about 480 V/mm, non linear coefficient reaching 44 and leakage current of 0.7 μA.

Appropriate Conditions for Preparation of Nanosized WO3 through High-Energy-Milling

2011 ◽  
Vol 194-196 ◽  
pp. 665-668
Author(s):  
Chun Huan Chen ◽  
Rui Ming Ren
Keyword(s):  
Grain Size ◽  
Milling Time ◽  
Rotation Speed ◽  
Processing Parameters ◽  
High Energy ◽  
Charge Ratio ◽  
Activation Process ◽  
X Ray Diffraction ◽  
High Energy Milling ◽  
Transmission Electron

In order to synthesize WC-Co nanopowders through an integrated mechanical and thermal activation process, WO3-Co2O3-C nanopowders need to be obtained first. It is critical how to obtain the WO3-Co2O3-C nanopowders efficiently. The effect of processing parameters on the grain size during high-energy-milling of WO3-Co2O3-C mixed powders was studied via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the grain size of reactants can be effectively decreased with increasing the milling time, rotation speed, and charge ratio. After a certain time milling, both WO3 and C powders achieve nano-level in grain size and mixed homogeneously. The appropriate milling parameters for fabricating nanosized WO3+C+Co2O3 powders are suggested to be 4 to 8 hours of milling time, 400 RPM of rotation speed, and 40:1 to 60:1 of charge ratio.

Effect of Sintering Temperature on Electrical Properties of ZnO Varistor Ceramics

2012 ◽  
Vol 442 ◽  
pp. 31-34
Author(s):  
Chang Qi Xia ◽  
Qi Bin Liu ◽  
Mo He
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Leakage Current ◽  
High Voltage ◽  
Sintering Temperature ◽  
Voltage Gradient ◽  
Varistor Ceramic ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Ceramic Sintering

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135～1155 °C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 °C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8μA and the density is 96.4%. When the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%. Compared the results at 1135 °C with 1140 °C , it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 °C.

scholarly journals Effect of starting materials and sintering temperature on microstructure and optical properties of Y2O3:Yb3+ 5 at% transparent ceramics

2020 ◽  
Author(s):  
R. P. Yavetskiy ◽  
A. E. Balabanov ◽  
S. V. Parkhomenko ◽  
O. S. Kryzhanovska ◽  
A. G. Doroshenko ◽  
...  
Keyword(s):  
Grain Size ◽  
Optical Properties ◽  
Sintering Temperature ◽  
Raw Materials ◽  
High Energy ◽  
Reactive Sintering ◽  
Average Grain Size ◽  
Median Particle ◽  
Energy Ball ◽  
Sintering Method

Abstract Y2O3:Yb3+ 5 at% ceramics have been synthesized by the reactive sintering method using different commercial yttria powders (Alfa-Micro, Alfa-Nano, and ITO-V) as raw materials. It has been shown that all Y2O3 starting powders consist from agglomerates up to 5–7 µm in size which are formed from 25–60 nm primary particles. High-energy ball milling allows to significantly decreasing the median particle size D50 below 500 nm regardless of the commercial powders used. Sintering experiments indicate that powder mixtures fabricated from Alfa-Nano yttria powders have the highest sintering activity, while (Y0.86La0.09Yb0.05)2O3 ceramics sintered at 1750 °C for 10 h are characterized by the highest transmittance of about 45%. Y2O3:Yb3+ ceramics have been obtained by the reactive sintering at 1750–1825°C using Alfa-Nano Y2O3 powders and La2O3+ZrO2 as a complex sintering aid. The effects of the sintering temperature on densification processes, microstructure, and optical properties of Y2O3:Yb3+ 5 at% ceramics have been studied. It has been shown that Zr4+ ions decrease the grain growth of Y2O3:Yb3+ ceramics for sintering temperatures 1750–1775 °C. Further increasing the sintering temperature was accompanied by a sharp increase of the average grain size of ceramics referred to changes of structure and chemical composition of grain boundaries, as well as their mobility. It has been determined that the optimal sintering temperature to produce high-dense yttria ceramics with transmittance of 79%–83% and average grain size of 8 µm is 1800 °C. Finally, laser emission at ∼1030.7 nm with a slope efficiency of 10% was obtained with the most transparent Y2O3:Yb3+ 5 at% ceramics sintered.

Effect of B2O3 Doping on the Microstructure and Electrical Properties of ZnO-Based Varistors

2008 ◽  
Vol 368-372 ◽  
pp. 497-499 ◽  
Author(s):  
Feng Hua Liu ◽  
Gao Jie Xu ◽  
Lei Duan ◽  
Ya Li Li ◽  
Ping Cui
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Solid State Reaction Method ◽  
Electrical Measurements ◽  
Conventional Solid State Reaction ◽  
Reaction Method ◽  
B2o3 Content ◽  
Zno Varistors ◽  
Doped Zno

B2O3 doped ZnO-Bi2O3-Sb2O3-based varistors were fabricated by conventional solid state reaction method. The structure and electrical properties were investigated by XRD, SEM and electrical measurements. The grain size obviously increases with increasing B2O3 content, while the content of Zn7Sb2O12 spinel on the grain boundaries gradually decreases, which implies that B2O3 doping inhibits the growth of Zn7Sb2O12 spinel. The density (ρ) of ZnO varistors increases with increasing B2O3 content (x) and reaches the maximum at x = 0.4 mol%. The sample with x ≈ 0.6 mol% sintered at 1150 °C exhibits the best performance, with nonlinear coefficient of 48 and leakage current of 4 μA.

Effect of High-Energy Milling and Sintering Temperature on the Properties of Al2O3-WC-Co Composites

2021 ◽  
Author(s):  
Heytor V. S. B. Azevêdo ◽  
Rafael A. Raimundo ◽  
David D. S. Silva ◽  
Luís M. F. Morais ◽  
Franciné A. Costa ◽  
...  
Keyword(s):  
Sintering Temperature ◽  
High Energy ◽  
High Energy Milling

Preparation and Electrical Property of Calcia Stabilized Zirconia Ceramics

2014 ◽  
Vol 616 ◽  
pp. 157-165 ◽  
Author(s):  
Chang Lian Chen ◽  
Hong Quan Wang ◽  
Jia You Ji ◽  
Ma Ya Luo ◽  
Bo Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Electrical Property ◽  
Arrhenius Equation ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Cubic Phase ◽  
Pressureless Sintering ◽  
Stabilized Zirconia ◽  
Zirconia Ceramics ◽  
Sintering Method

In this paper, using ZrO2 and Ca (NO3)•4H2O as raw materials, we prepared a series of calica stabilized zirconia (CSZ) ceramics by pressureless sintering method. The results show that the relative densities of all sintered samples are above 90%, and the sintered samples are composed of cubic, tetragonal and monoclinic ZrO2, and the main phase is cubic ZrO2 and tetragonal ZrO2. The content of cubic phase increases with the increase of sintering temperature and adding CaO content. The grain size of the sintered samples is relatively uniform and some pores exist. Increasing the additive amount of CaO, the conductivity first rises and then decreases, and the conductivity value of the sample containing 5wt% CaO is the maximum. When the sintering temperature is up to 1600 oC, the conductivity of the sample containing 5wt% CaO is up to 0.016S•cm-1 at 800 oC. Furthermore, the conductivity of sintered samples is increasing with the increase of test temperature according to the Arrhenius equation.

scholarly journals Influence of mechanical activation of AL2O3 on synthesis of magnesium aluminate spinel

2004 ◽  
Vol 36 (2) ◽  
pp. 73-79 ◽  
Author(s):  
Zhang Zhihui ◽  
LI. Nan
Keyword(s):  
Grain Size ◽  
Mechanical Activation ◽  
Bulk Density ◽  
Milling Time ◽  
High Energy ◽  
Magnesium Aluminate ◽  
Reaction Sintering ◽  
Air Atmosphere ◽  
Energy Ball ◽  
Analytical Reagent

Magnesium aluminate (MA) spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.

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