scholarly journals Correlation between chemical composition of the γ-Bi2O3 phase and the properties of ZnO varistors

2005 ◽  
Vol 11 (4) ◽  
pp. 169-172 ◽  
Author(s):  
Zorica Brankovic ◽  
Goran Brankovic ◽  
Dejan Poleti ◽  
Ljiljana Karanovic ◽  
Jose Varela
Keyword(s):  
Phase Composition ◽  
Chemical Composition ◽  
Electrical Properties ◽  
Leakage Current ◽  
Diffusion Processes ◽  
Lattice Constants ◽  
Eds Analysis ◽  
Phase Spinel ◽  
Zno Varistors

Four varistor samples differing in chemical and phase composition of the starting Bi2O3 phase were prepared by the method of direct mixing of the constituent phases (DMCP), i.e. by sintering the mixture of the previously prepared phases. The compositions of the constituent phases in the sintered samples were investigated by changes of their lattice constants and by EDS analysis. After sintering, the phase compositions of all the investigated samples were the same: ZnO phase, spinel and ?-Bi2O3. It was found that the ?-Bi2O3 phase was mainly stabilized with Zn2+ ions. All the samples showed good electrical properties with non-linearity coefficients up to 50 and small values of the leakage current. The electrical properties of the samples were discussed in terms of diffusion processes and the redistribution of additives during sintering.

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 Technological Parameters on the Microstructure and Electrical Properties of ZnO Varistors

2013 ◽  
Vol 820 ◽  
pp. 208-211
Author(s):  
Li Li ◽  
Qi Bin Liu
Keyword(s):  
Solid State ◽  
Electrical Properties ◽  
Leakage Current ◽  
Sintering Temperature ◽  
Voltage Gradient ◽  
Technological Parameters ◽  
Reaction Route ◽  
Conventional Solid State Reaction ◽  
Zno Varistors ◽  
Solid State Reaction Route

To improve voltage-gradient and to reduce the sintering temperature of ZnO varistors, high voltage-gradient ZnO varistors were synthesized with a conventional solid state reaction route. By means of SEM and DC parameter instrument for varistor, the influence of different technological parameters on microstructure, voltage-gradient and leakage current of ZnO varistors was investigated. The experimental results show that by using the process that presintering the additives at 850°C, the density is improved, the voltage-gradient is increased, and the leakage current is decreased. The optimum voltage-gradient and leakage current are 371V/mm and 3μA, respectively.

The Electrical Properties and Impedance Analysis of ZnO Varistors Doped with Different Cu2O Contents

2014 ◽  
Vol 681 ◽  
pp. 173-176
Author(s):  
Ji Wei Fan ◽  
Hui Jun Zhao ◽  
Xiao Li Zhang
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Leakage Current ◽  
Impedance Analysis ◽  
Boundary Resistance ◽  
Zno Varistors ◽  
Good Agreement

The Cu2O addition deteriorates the electrical properties of ZnO varistors, which is a good agreement with similar findings on Ag2O additions. The best fitted impedance analysis reveals that the Cu2O addition increases grain resistance and lowers the grain boundary resistance, results in low nonlinearity and higher leakage current of ZnO varistors.

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 Electrochemical deposition and characterization of Ni-Mo alloy powders

2007 ◽  
Vol 1 (1-2) ◽  
pp. 11-17
Author(s):  
M.G. Pavlovic ◽  
B.M. Jovic ◽  
V.D. Jovic ◽  
U. Lacnjevac ◽  
V.M. Maksimovic
Keyword(s):  
Phase Composition ◽  
Chemical Composition ◽  
Concentration Ratio ◽  
Xrd Analysis ◽  
Crystalline Powder ◽  
Powder Composition ◽  
Eds Analysis ◽  
N2 Atmosphere ◽  
Powder Particles

Electrodeposition of Ni-Mo alloy powders from ammonium sulfate and ammonium chloride containing electrolytes of different Ni/Mo ions concentration ratios was investigated by polarization measurements. The morphology, chemical composition and phase composition of electrodeposited Ni-Mo alloy powders were investigated using DSC, TGA, SEM, EDS and XRD analysis. EDS results showed that powder composition depends on Ni/Mo ions concentration ratio, as well as on the position where the EDS analysis was performed. As-deposited alloy powders were nanocrystalline showing no XRD peaks with undefined morphology (SEM). After recrystallization for 2 h in N2 atmosphere at 600?C the presence of NiMoO4 phase was identified in the powder electrodeposited from chloride electrolyte at the Ni/Mo ions concentration ratio 1/3, with well defined crystalline powder particles.

Diffusion Niobizing of Titanium Grade 2 by Gas-Contact Method

2015 ◽  
Vol 669 ◽  
pp. 158-166
Author(s):  
Dariusz Bartkowski ◽  
Andrzej Mlynarczak ◽  
Adam Piasecki ◽  
Waldemar Matysiak ◽  
Michal Hatala ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Diffusion Layer ◽  
Powder Mixture ◽  
Diffusion Processes ◽  
Contact Method ◽  
Niobium Content ◽  
Structure Quality ◽  
Pure Niobium ◽  
Titanium Grade ◽  
Geometric Surface

The work presents results of diffusion niobizing of titanium Grade 2 by gas-contact method. Microhardness, thickness, chemical composition and microstructure were investigation. Diffusion processes was carried out in a two powder mixture. First consisted of ferro-niobium, kaolin and ammonium chloride, second mixture contained pure niobium instead ferro-niobium. The processes were carried out at 950°C, 1000°C and 1050°C for 2, 4 and 6 hours. Due to the geometric surface structure quality and other properties like thickness or microhardness, the best diffusion layer was obtained using first powder mixture and following parameters: temperature 950°C and time of diffusion equal 2 hours. The diffusion layer established in these conditions, had structure of niobium solution in titanium, and niobium content of about 10%. Its hardness was 550 HV0.05 while thickness was 120 μm.

Mechanical Property of Phosphoaluminate Cement

2010 ◽  
Vol 150-151 ◽  
pp. 1754-1757 ◽  
Author(s):  
Peng Liu ◽  
Zhi Wu Yu ◽  
Ling Kun Chen ◽  
Zhu Ding
Keyword(s):  
Mechanical Property ◽  
Compressive Strength ◽  
Phase Composition ◽  
Electrical Properties ◽  
Pore Size Distribution ◽  
Pore Size ◽  
High Strength ◽  
Curing Time ◽  
Hydration Products ◽  
Resistance Value

The influence of curing time on the mechanical property of the phosphoaluminate cement (PAC) was investigated, and the mechanism was discussed as well. The phase composition and morphology of hydration products, electrical properties, porosity and pore size distribution of PAC cured different age were analyzed with XRD, EIS and MIP. The results showed PAC has the property of early-high strength, and the compressive strength of PAC cured for 1 day was about 70% of 28 days’. The main hydration products of PAC are micro-crystal phase and gel of phosphate and phosphoaluminate which formed compacter microstructure. In addition, there are no calcium hydroxide (CH) and ettringite (AFt) produced during the process of hydration. The compressive strength of PAC increased with age, which was due to more products continuously produced. The ac resistance analysis manifested as the change of the nyquist pattern and resistance value.

Thermal Acclimation of a Central Neurone in Helix Aspersa: III. Ionic Substitution and Related Studies

1979 ◽  
Vol 78 (1) ◽  
pp. 201-211
Author(s):  
C. K. LANGLEY
Keyword(s):  
Chemical Composition ◽  
Electrical Properties ◽  
Membrane Resistance ◽  
Thermal Acclimation ◽  
Neuronal Membrane ◽  
Electrical Characteristics ◽  
Ionic Substitution ◽  
Warm Acclimation ◽  
Sodium And Potassium ◽  
Made In

(1) Thermal acclimation of the Fi neurone does not appear to result from changes in the chemical composition of the haemolymph. This is deduced from the lack of effect on the electrical characteristics of control neurones of either pooled haemolymph from acclimated individuals, or variations in the experimental salines made in accordance with haemolymph analyses. (2) Changes in [Ca]0 tended to act cooperatively with temperature shifts to induce alterations in the electrical properties of the neurone, notably to increase excitability and lower membrane resistance. (3) Warm acclimation was associated with increased resting conductance of the neuronal membrane to sodium and potassium, whereas chloride conductance appeared little affected.

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