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.

scholarly journals Structural and Electrical Properties of ZnO Varistor with Different Particle Size for Initial Oxides Materials

2019 ◽  
Vol 2 (2) ◽  
pp. 20-31 ◽  
Author(s):  
Susan A Amin
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Nonlinear Coefficient ◽  
Hexagonal Wurtzite Structure ◽  
The Other ◽  
Breakdown Field ◽  
Residual Voltage ◽  
Structural And Electrical Properties ◽  
Increasing Temperature ◽  
Initial Starting

We report here structural, electrical and dielectric properties of ZnO varistors prepared with two different particle sizes for initial starting oxides materials (5 µm and 200 nm). It is found that the particle size of ZnO does not influence the hexagonal wurtzite structure of ZnO, while the lattice parameters, crystalline diameter, grain size and Zn-O bond length are affected. The nonlinear coefficient, breakdown field and barrier height are decreased from 18.6, 1580 V/cm and 1.153 eV for ZnO micro to 410 V/cm, 7.26 and 0.692 eV for ZnO nano.  While, residual voltage and electrical conductivity of upturn region are increased from 2.08 and 2.38x10-5 (Ω.cm)-1 to 4.55 and 3.03x10-5 (Ω.cm)-1. The electrical conductivity increases by increasing temperature for both varistors, and it is higher for ZnO nano than that of ZnO micro.  The character of electrical conductivity against temperature is divided into three different regions over the temperature intervals as follows; (300 K ≤ T ≤ 420 K), (420 K ≤ T ≤ 580 K) and (580 K ≤ T ≤ 620 K), respectively. The activation energy is increased in the first region from 0.141 eV for ZnO micro to 0.183 eV for ZnO nano and it is kept nearly constant in the other two regions. On the other hand, the average conductivity deduced through dielectric measurements is increased from 2.54x10-7 (Ω.cm)-1 for ZnO micro to 49x10-7 (Ω.cm)-1. Similar behavior is obtained for the conductivities of grains and grain boundaries. The dielectric constant decreases as the frequency increases for both varistors, and it is higher for ZnO nano than that of ZnO micro. These results are discussed in terms of free excited energy and strength of link between grains of these varistors.

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.

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.

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.

Structural and electrical properties of ZnO/Zn0.85Mg0.15O thin film prepared by pulsed laser deposition

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744056 ◽  
Author(s):  
Jing-Jing Yang ◽  
Gang Wang ◽  
Wen-Han Du ◽  
Chao Xiong
Keyword(s):  
Electrical Properties ◽  
Electrical Transport ◽  
Lattice Structure ◽  
Quantum Effect ◽  
Impurity Scattering ◽  
Hexagonal Wurtzite Structure ◽  
Electrical Transport Properties ◽  
Typical Material ◽  
Structural And Electrical Properties ◽  
Dimensional Electron Gas

The electrical transport properties are the key factors to determine the performance of ZnO-based quantum effect device. ZnMgO is a typical material to regulate the band of ZnO. In order to investigate the electrical properties of the interface of ZnO/Zn[Formula: see text]Mg[Formula: see text]O films, three kinds of ZnO/Zn[Formula: see text]Mg[Formula: see text]O films have been fabricated with different thickness. After comparing the structural and electrical properties of the samples, we found that the independent Zn[Formula: see text]Mg[Formula: see text]O hexagonal wurtzite structure (002) peak can be detected in XRD spectra. Hall-effect test data confirmed that the two-dimensional electron gas (2DEG) became lower because of the decrease of thickness of Zn[Formula: see text]Mg[Formula: see text]O films, increase of impurity scattering and lattice structure distortion caused by the increase of Mg content.

Electrical Properties of a TiO2-SrO Varistor System

2014 ◽  
Vol 975 ◽  
pp. 168-172
Author(s):  
Tiago Delbrücke ◽  
Igor Schmidt ◽  
Sergio Cava ◽  
Vânia Caldas Sousa
Keyword(s):  
Titanium Dioxide ◽  
Electrical Properties ◽  
Field Strength ◽  
Leakage Current ◽  
Low Voltage ◽  
Nonlinear Coefficient ◽  
Breakdown Field ◽  
Strontium Oxide ◽  
Breakdown Field Strength

The addition of different dopants affects the densification and electrical properties of TiO2 based varistor ceramics. The nonlinear current (I) and voltage (V) characteristics of titanium dioxide are examined when doped with small quantities (0.5-2 at.%) of strontium oxide. This paper discusses the electrical properties of such an SrO doped TiO2 system, and demonstrates that some combinations produce electrical properties suitable for use as low voltage varistors. The high value of the nonlinear coefficient (α) (6.6), the breakdown field strength (Eb) (328 V/cm) and the leakage current (Ir) (0.22 mA/cm2) obtained in a system newly doped with SrO, are all adequate properties for application in low voltage varistors.

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.

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.

Structural and Electrical Properties of ZnTe Thin Films Deposited at Various Substrate Temperatures

2013 ◽  
Vol 665 ◽  
pp. 80-84
Author(s):  
J.R. Gandhi ◽  
K.D. Patel ◽  
G.K. Solanki
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Structural Parameters ◽  
Hall Effect Measurement ◽  
Xrd Analysis ◽  
Electrical Parameters ◽  
Glass Substrates ◽  
Structural And Electrical Properties ◽  
Substrate Temperatures ◽  
Znte Thin Films

The structural and electrical properties of ZnTe thin films were investigated as a function of substrate temperature. Vacuum evaporated thin films of Zinc Telluride (ZnTe) of 10kÅ thickness have been deposited on ultrasonically cleaned glass substrates at various substrate temperatures (303K, 373K 448K). Structural parameters were obtained using XRD analysis. It was observed that the films deposited were cubic in nature with a strong (111) texture. Electrical parameters (Hall Effect measurement) have been obtained and studied at various temperatures in the range 303-393K. It is observed that Hall coefficient remains positive throughout the whole temperature range indicating that holes are the majority carriers. The results obtained from structural and electrical parameters study have been correlated and it is found that the thin films deposited at higher substrate temperatures possess increasingly good crystalline structure with improved electrical conductivity along with an increase in carrier concentration and mobility of carriers.

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