scholarly journals A Comparative Study between the Effects of Magnetic and Nonmagnetic Dopants on the Properties of ZnO Varistors

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
A. Sedky ◽  
E. El-Suheel
Keyword(s):  
Comparative Study ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Breakdown Field ◽  
Doping Content ◽  
Leakage Currents ◽  
Electrical Conductivities ◽  
Zno Varistors ◽  
The Difference ◽  
Zno Ceramics

A comparative study between effects of Mn and Al on the properties of ZnO varistor sintered at 1200 is investigated by XRD, SEM hardness, and I-V measurements. Although both Mn and Al do not influence the well-known peaks related to wurtzite structure of ZnO ceramics, some other unknown peaks could be formed at higher doping content (). Also, the shape and size of grains are clearly different for both dopants. Average crystalline diameters, deduced from XRD analysis, are between 42 nm and 62 nm, which are 50 times lower than those obtained from SEM micrographs, while the oxygen vacancies deduced from EDAX analysis, are gradually decreased by doping content for both dopants. Interestingly, the values of breakdown field, nonlinear coefficient and barrier height are found to be higher in Mn samples as compared to Al samples, while the opposite is reported for leakage currents, hardness, and electrical conductivities. The values of are changed from 2.67 V/cm to 41.67 V/cm for Al, and from 1928 V/cm to 6571 V/cm for Mn. The conductivity of Al samples is higher than that of ZnO, and it is nearly (103–105) times the conductivity of Mn samples. These results are discussed in terms of the difference of magnetic moment and valence state between these two additives.

scholarly journals Fabrication and electrical characteristics of flash-sintered SiO2-doped ZnO-Bi2O3-MnO2 varistors

2020 ◽  
Author(s):  
Pai Peng ◽  
Jingpeng Niu ◽  
Liyi Shi ◽  
Yunzhu Mei ◽  
Sanming Du ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Oxygen Absorption ◽  
Doping Content ◽  
Electrical Characteristics ◽  
Secondary Phases ◽  
Ion Migration ◽  
Average Grain Size ◽  
Structure Density

Abstract The dense ZnO-Bi 2 O 3 -MnO 2 - x SiO 2 (ZBMS) varistors were fabricated by flash sintering method under the low temperature of 850 o C within 2 minutes. The phase structure, density, microstructure, and electrical characteristics of the flash-sintered ZBMS varistors with different SiO 2 doping content were investigated. According to the XRD analysis, many secondary phases were detected due to the doping of SiO 2 . Meanwhile, the average grain size decrease with increasing SiO 2 doping content. In addition, the electrical properties of all samples were analyzed. The improved nonlinear characteristics were obtained in SiO 2 doped samples, which can be attributed to the ion migration and oxygen absorption induced by the doping of SiO 2 . The flash-sintered ZBMS varistor ceramics exhibited excellent comprehensive electrical properties, with the nonlinear coefficient of 24.5, the threshold voltage and leakage current of 385 V/mm and 11.8 µA, respectively.

scholarly journals Effect of Temperature and Magnetic Dopants on Particle size and Electrical Properties of ZnO Ceramic Varistor

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Hexagonal Wurtzite Structure ◽  
Xrd Analysis ◽  
Effect Of Temperature ◽  
Breakdown Field ◽  
Valence States ◽  
Structural And Electrical Properties ◽  
Ionic Emission ◽  
Fesem Micrographs

We report here structural and electrical properties of Zn0.95 M0.05O ceramic, M = Zn, Co and Mn. It is found that addition of magnetic doping did not influence the hexagonal wurtzite structure of ZnO. Furthermore, the lattice parameters ratio c/a for hexagonal distortion and the length of the bond parallel u to the c axis were nearly unaffected. The average crystalline diameters, deduced from XRD analysis are 83.75, 72.86 and 70.97 nm for Zn, Mn and Co, which are 15 times lower than those obtained from FESEM micrographs (1570, 1380 and 1150 nm). The breakdown field EB was decreased as the temperature increased, in the following order: Mn> Zn > Co. The nonlinear region was observed for all samples as the temperature increased up to 400 K and completely disappeared with further increase of temperature up to 500 K. The values of nonlinear coefficient, α were between 1.65 and 56 for all samples, in the following order: Mn> Zn > Co. Moreover, the electrical conductivity σ was gradually increased as the temperature increased up to 500 K, in the following order: Co > Zn > Mn. On the other hand, the activation energies were 0.194, 0.155 eV and 0.231 eV for all samples, in the following order Mn, Zn and Co. These results have been discussed in terms of valence states, magnetic moment and thermo-ionic emission which were produced by the doping, and controlling the potential barrier of ZnO.

Analyses of defect distributions in ZnO varistors based on the Jonscher’s universal power law and the Dissado–Hill model

2021 ◽  
Vol 55 (13) ◽  
pp. 135106
Author(s):  
Xia Zhao ◽  
Men Guo ◽  
Yuandong Wen ◽  
Weidong Shi ◽  
Boyu Zhang ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Power Law ◽  
Current Density ◽  
Nonlinear Coefficient ◽  
Breakdown Field ◽  
Hill Model ◽  
X Ray ◽  
Universal Power Law ◽  
Zno Varistors ◽  
Doped Zno

Abstract The defect distributions in ZnO varistors mixed with Bi2O3, NiO, MnCO3, Co2O3, and SiO2 after doping Sb2O3 were investigated, based on the Jonscher’s universal power law and the Dissado–Hill model. The microstructures were investigated using x-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, and x-ray photoelectron spectrometer. The capacitance–voltage (C–V) method was utilized to obtain the parameters of the double Schottky barrier. The dielectric spectra were analyzed to extract the parameters of defect distribution. The current density–electric field (J–E) characteristics were measured to obtain the parameters of electrical properties. We found that with increasing Sb2O3 content, the ZnO grain size distribution become more homogeneous in the Sb2O3-doped ZnO varistors; the density Zn i × is decreased; except for less homogeneous V O × , more homogeneous distributions of Zn i ∙ in the depletion layers and the extrinsic defects at the interfaces are achieved in the Sb2O3-doped ZnO varistors. Therefore, the enhancement in the electrical properties was achieved by doping Sb2O3 due to the increased number of active grain boundaries per unit volume, i.e. the increased breakdown field and nonlinear coefficient, and the decreased leakage current density. The results of this study suggest that the Jonscher’s universal power law and the Dissado–Hill model can be effectively used to analyze defect distributions in varistor ceramics.

scholarly journals Influence of Fine Crystal Percentage on the Electrical Properties of ZnO Ceramic-Based Varistors

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 681 ◽  
Author(s):  
Abdullah Aljaafari ◽  
Ahmed Sedky
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Nonlinear Coefficient ◽  
Average Crystallite Size ◽  
Hexagonal Wurtzite Structure ◽  
Xrd Analysis ◽  
Breakdown Field ◽  
Zno Nanostructures ◽  
Electrical Measurements ◽  
Fine Crystal

Herein, the effect of nanocrystal percentage in bulk-ZnO varistors was studied. The structure of ZnO nanocrystals was examined using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The XRD studies showed that the nanocrystals were indexed with the hexagonal wurtzite structure of ZnO nanostructures. The average crystallite size deduced from XRD analysis ranged between 135 and 273 nm, eight-fold lower than that of the nanoparticles observed in FE-SEM micrographs (1151–2214 nm). The percentage of nanocrystals added into the ZnO varistor was increased from 0 to 100%. Electrical measurements (I–V profiles) showed that the non-linear region, breakdown field, and activation energy were found to decrease with the addition of ZnO fine crystals up to 10% and then increased upon a further increase in fine crystals. However, the electrical conductivity measured at room temperature was improved, and the highest value of 2.11 × 10−5 was observed for 10% fine crystals and then decreased upon a further increase in the fine crystal concentration in bulk ZnO. The breakdown field decreased with the increase in the percentage of ZnO nanostructures in the varistor up to 10% and then increased upon the further addition of ZnO nanostructures. The nonlinear coefficient (α) was decreased from 18.6 for bulk ZnO and remained close to unity for the samples that contained fine crystals. The electrical conductivity was generally improved with the increase in the concentration of the ZnO fine crystals. The activation energy was found to be 128, 374, and 815 meV for the bulk samples and 164, 369, and 811 meV for the samples that contained 100% fine crystals for the three temperature regions of 300–420, 420–580, and 580–620 K, respectively. These results will provide a pathway toward the determination of a correlation between the electrical and microstructural properties of ZnO-based varistors for future device applications.

Comparative Study of Size, Total Protein, Fibrinogen and 5-HT Content of Human and Canine Platelet Density Subpopulations

1986 ◽  
Vol 56 (03) ◽  
pp. 288-292 ◽  
Author(s):  
Diego Mezzano ◽  
Eduardo Aranda ◽  
Arnaldo Foradori
Keyword(s):  
Comparative Study ◽  
Protein Content ◽  
Cell Density ◽  
Total Protein ◽  
Unit Volume ◽  
Low Density ◽  
Dense Bodies ◽  
Artifactual Changes ◽  
Platelet Release ◽  
The Difference

SummaryThe size, total protein, fibrinogen and 5-HT content were evaluated in density subpopulations of human and canine platelets fractionated in linear arabinogalactan gradients. The methodology was assessed to ascertain that platelet separation was by density and to discard artifactual changes and platelet release during the procedure. EDTA or PGEi increased the size of human PRP-platelets, but not of dog platelets. In humans, high density (HD) platelets were 1.26 times larger and contained 1.88 times more fibrinogen, 2.23 times more 5-HT and 1.37 times more protein than low density (LD) platelets; in dogs, these density cohorts did not differ in protein content, but LD platelets were 1.29 times larger and had 1.33 times more fibrinogen and 5-HT than HD platelets. These findings suggest that cell density is mostly dependent on the protein content per unit volume of platelets (and not on dense bodies). The differences in fibrinogen and 5-HT content between HD and LD cohorts in humans and dogs may be related to platelet age. The difference in volume between HD and LD platelets in dogs is of uncertain interpretation.

Pandhawa Gubah sebagai Representasi Interaksi Metafisik Manusia Jawa dan Perbandingannya dengan Cheritera Pandawa Lima

Manuskripta ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 67
Author(s):  
Novarina Novarina
Keyword(s):  
Comparative Study ◽  
Literary Theory ◽  
Research Method ◽  
Descriptive Analysis ◽  
Literary Study ◽  
Analysis Method ◽  
Research Objects ◽  
Similarities And Differences ◽  
The Difference ◽  
The Comparative Study

Abstract: This research is a comparative literary study that uses Malay and Javanese versions of Mahabarata text sources. The research objects used were the text edition of Pandhawa Gubah (PG) by Sudibjo Z. Hadisutjipto and the text of Cheritera Pandawa Lima (CPL) by Khalid Hussain. The research method used is descriptive-analysis method. In the comparative study used a comparative literary theory proposed by Endraswara (2011). The results of the text comparison reveal the similarities and differences in the image of Bima figures in the Javanese and Malay versions. The equation as a whole is that both texts contain the same heroic storyline and heroic character, Bima. In addition, Indian influence is still evident in the two texts seen from the nuances of Hinduism that exist in both texts. While the difference is seen in the events that accompany Bima's struggle in achieving his victory. Based on these similarities and differences, it can be seen that the authors attempt to represent the concept of metaphysical interactions vertically and horizontally expressed through PG text. --- Abstrak: Penelitian ini adalah satu kajian sastra bandingan yang menggunakan sumber teks Mahabarata versi Melayu dan Jawa. Objek penelitian yang digunakan adalah edisi teks Pandhawa Gubah (PG) karya Sudibjo Z. Hadisutjipto dan teks Cheritera Pandawa Lima (CPL) karya Khalid Hussain. Metode penelitian yang digunakan adalah metode deskriptif-analisis. Dalam telaah perbandingan digunakan teori sastra bandingan yang dikemukakan Endraswara (2011). Hasil perbandingan teks mengungkapkan adanya persamaan dan perbedaan citra tokoh Bima dalam versi Jawa maupun versi Melayu. Persamaan secara keseluruhan adalah kedua teks tersebut mengandung alur cerita kepahlawanan dan tokoh pahlawan yang sama yaitu Bima. Selain itu, pengaruh India masih tampak dalam kedua teks tersebut dilihat dari nuansa Hinduisme yang ada dalam kedua teks. Sementara perbedaannya tampak pada peristiwa-peristiwa yang menyertai perjuangan Bima dalam mencapai kemenangannya. Berdasarkan persamaan dan perbedaan tersebut tampak adanya upaya penulis untuk merepresentasikan konsep interaksi metafisik secara vertikal dan horizontal yang diungkapkan melalui teks PG.

Being Mother:Comparative Study of the Contested Motherhood between South Korea and Indonesia

2018 ◽  
Vol 1 (1) ◽  
pp. 22
Author(s):  
Desintha Asriani
Keyword(s):  
Political Economy ◽  
South Korea ◽  
Comparative Study ◽  
Cultural Issues ◽  
Family Routine ◽  
The Difference

This paper attempts to explain the discourse of motherhood in both South Korea and Indonesia. It is based on the interesting dynamic of being mother that is much influenced by the interrelated actions played by number of dominant actors around woman itself. By using a comparative study, it is found that the map or the trace of political economy in terms of developmental agenda, in fact drives the difference flows in shaping the notion of motherhood. In Indonesia, for being mother, women exist in the intersection of state intention, industrialization and culture pressure. Indonesian motherhood is interestingly in line with another analysis, such in their relation with housemaids. Meanwhile, in South Korea, the description of motherhood occurs in the middle of nationalism spirit, competition, ambience and family routine. Hence, this study concludes that being mother is highly contested and closely associated with the endless structural and cultural issues.

Comparative study of hemodynamic effects, quality of extubation and emergence - agitation response of the patients with dexmedetomidine versus lignocaine during and following the endotracheal extubation

2021 ◽  
Vol 19 (3) ◽  
pp. 91-95
Author(s):  
Manasi Panat ◽  
Keyword(s):  
Comparative Study ◽  
Stress Responses ◽  
Tracheal Extubation ◽  
Emergence Agitation ◽  
Quality Of Recovery ◽  
Group 12 ◽  
The Difference ◽  
Group D ◽  
Endotracheal Extubation

Background: Endotracheal extubation is the translaryngeal removal of a tube from the trachea via the nose or mouth. It is associated with hemodynamic changes because of reflex sympathetic discharge caused by epipharyngeal and laryngopharyngeal stimulation. Various drugs and techniques have been tried to attenuate the airway and stress responses during tracheal extubation. In present study, we have compared the effects of dexmedetomidine and intravenous lignocaine on the hemodynamic and recovery profiles during endotracheal extubation. Material and Methods: Present study was prospective randomised comparative study, conducted in patients from age group of 18-45 years, ASA grade I/II, scheduled for elective abdominal surgeries. The patients were categorised into two different groups using the sealed envelope method as Group D and group L. Results: In present study, patients were divided in following 2 groups with 50 patients in each group as group D (Dexmedetomidine) and group L (Lignocaine). Age, gender, mean BMI were comparable in both groups and difference was not significant statistically. The difference between mean heart rate, systolic BP, diastolic BP and mean arterial BP during extubation, after extubation at 1, 3, 5, 10, 15, 20, 25, 30 minutes in dexmedetomidine group and lignocaine group was statistically significant. In Dexmedetomidine group, 12% of the patients had no cough during extubation, 72% of the patients had smooth extubation with minimal cough while in Lignocaine group, 22% of the patients had smooth extubation with minimal cough, 74 % of the patients had moderate cough during extubation. Statistical analysis of the Emergence agitation score shows better results in group D. Conclusion: Administration of Dexmedetomidine before tracheal extubation was more effective in maintaining the hemodynamic stability, facilitated smooth tracheal extubation and had a better quality of recovery as compared to Lignocaine.

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