scholarly journals Mechanical behavior and electrical conductivity of zinc-oxide ceramics

2020 ◽  
Vol 2020 (01) ◽  
pp. 46-54
Author(s):  
Y. M. Ostroverkh ◽  
◽  
I. O. Polishko ◽  
D. M. Brodnikovskyi ◽  
L. L. Kovalenko ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Zinc Oxide ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Type I ◽  
Type Ii ◽  
Conductivity Activation Energy ◽  
Zno Powder ◽  
Zno Ceramics

Ceramics sintered from zinc oxide powders, which differ in crystal structure, particle size and amount and type of impurities, have been studied for their mechanical behavior (strength and micromechanisms of biaxial bending at room temperature) and electrical conductivity depending on the purity of ZnO powder (99,9% byweight — type I and 99,5% byweight — type II) and its sintering temperature in the interval from 800 to 1250 ºC for 2 hours. It is found that the maximum values of strength and electrical conductivity are achieved in ZnO-ceramics sintered at temperatures of 1100—1200 and 1000—1150 ºC, respectively, and their micromechanism of fracture is the cleavage only. ZnO-powder developed (type II), being twice as large as the purchased (type I), 300—350 nm instead of 150—200 nm, provides close to 100% density at 1100 °C, the type II powder is sintering at almost 100 °C lower temperature than the purchased one. Type I ceramics provide biaxial strength at room temperature of 150—170 MPa; type II — 120—160 MPa. ZnO-ceramics from powders of both types provide maximum electrical conductivities of 8,54 10-3S/ cm and 1,6·10-3 S / cm at temperatures of 265 and 600 ºC, respectively. The activation energy of the electrical conductivity of ZnO-ceramics is dependent significantly on the properties of the powder and, accordingly, the structure of the ceramics and the test temperature. Type I ZnO ceramics have a lower conductivity activation energy than type II, 0,2—0,3 eVand 0,3—0,5 eV, respectively. The mechanism of electrical conductivity of ZnO-ceramics type I is practically unchanged in all the interval of testing temperatures, from the room one to 600 °C. In ZnO-ceramics of the type II, it changes at least twice. Keywords: zinc oxide, ZnO ceramics, sintering temperature, porosity, grain size, micromechanism of fracture, bending strength, electrical conductivity, activation energy.

ELECTRICAL PROPERTY OF CONVENTIONALLY SINTERED ZnO

2013 ◽  
Vol 22 ◽  
pp. 501-510 ◽  
Author(s):  
S. K. TAK ◽  
M. S. SHEKHWAT ◽  
R. MANGAL
Keyword(s):  
Sintering Temperature ◽  
Hold Time ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Phase Study ◽  
Average Grain Size ◽  
Structural And Electrical Properties ◽  
Different Temperatures ◽  
Zno Powder ◽  
Zno Ceramics

ZnO powder was synthesized by solid state reaction method. The synthesized powder was granulated and pressed using uni-axial press for preparing the pallets. The prepared pellets were sintered in conventional furnace at different temperatures (900-1300° C). The phase study was done by powder X-ray diffraction and it was found that the there is no other phase present in the synthesized material but the peak intensity is increasing with temperature. The crystallite size of the synthesized ZnO powder was found to be increase with temperature. The effect of sintering on grain growth is investigated by scanning electron microscopy (SEM). SEM revels that the average grain size is increases with increase in sintering temperature. AC impedance of these samples was decreased markedly with increased sintering temperature. In present work the effect of sintering temperatures and hold time on micro structural and electrical properties of ZnO ceramics is carried out.

Electrical Properties of n-GaN/p-SiC and n-AlGaN/p-SiC Heterojunction Diodes

2001 ◽  
Vol 693 ◽  
Author(s):  
B. Luo ◽  
J. Kim ◽  
R. Mehandru ◽  
F. Ren ◽  
K. P. Lee ◽  
...  
Keyword(s):  
Activation Energy ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Normal Type ◽  
Defect States ◽  
Dark Line ◽  
Continuous States ◽  
Line Defects ◽  
Heterojunction Diodes

AbstractProperties of n-GaN/p-SiC and n-AlGaN/p-SiC heterojunctions prepared by HVPE on 4H SiC substrates were studied by means of C-V, C/G-T, C-f, I-V and DLTS. It is shown, in agreement with earlier publications, that the GaN/p-SiC HJ is staggered type II with ΔEc=-0.4 eV andΔEv=0.6 eV. Whenchanging GaN for AlGaN with Al mole fraction of x=0.25-0.3 the band alignment becomes normal type I with ΔEc=0.2 eV andΔEv=0.6 eV. I-V characteristics of both heterojunctions bear evidence of strong tunneling via defect states, particularly centers with activation energy of 1.25 eV for GaN/4H SiC HJ. The tunneling was found to be more pronounced in the AlGaN/SiC HJs even though these HJs showed no evidence of formation of dark line defects at the interface, in contrast to GaN/SiC. DLTS measurements on both types of HJs revealed the presence of broad bands whose behavior is indicative of these bands being related to continuous states in the gap, most likely near the nitride/carbide interface.

Immittance Studies of DBP Plasticized Salicylic Acid Doped PMMA Based Gel Electrolytes

2006 ◽  
Vol 517 ◽  
pp. 97-100 ◽  
Author(s):  
M.I.N. Isa ◽  
S.R. Majid ◽  
A.K. Arof
Keyword(s):  
Activation Energy ◽  
Salicylic Acid ◽  
Room Temperature ◽  
Ethylene Carbonate ◽  
Gel Electrolyte ◽  
Electrolyte System ◽  
Conductivity Activation Energy ◽  
Gel Electrolytes ◽  
Tan Δ ◽  
Oxygen Site

A gel electrolyte system was prepared by dissolving poly(methyl methacrylate) in ethylene carbonate and propylene carbonate doped with salicylic acid and plasticized with dibutylphthalate (DBP). The gel was heated to 70 0C before it was cast into glass dishes. The composition of the electrolytes was 35 wt% EC, 30 wt% PC, 5 wt% SA, 5wt% DBP and 25 wt% PMMA. The gel electrolyte was sandwiched between two stainless-steel blocking electrodes and impedance measurements were conducted. The conductivity of the gel electrolyte was 2.03 x 10-4 S cm-1 at room temperature. The conductivity activation energy was obtained from the log σ versus 103/T graph. Loss tangent was calculated at every frequency for all temperatures. From the tan δ versus frequency plot, the activation energy of relaxation of the ion was calculated and plotted as ln τ versus 103/T. The conductivity activation energy value was (0.21 ± 0.04) eV and the activation energy of relaxation was (0.24±0.07) eV. The similarity between these activation energies imply that the protons ‘hop’ from one electronegative oxygen site in DBP to another.

scholarly journals Effect of SiO2 ratio on electrical Properties of SiO2:ZnO Thin Films Prepared by pulsed laser depositions (PLD) technique

2019 ◽  
Vol 23 (10) ◽  
pp. 76
Author(s):  
Abdul-Majeed E. Al-Samarai1 ◽  
Zuheer. N. Majeed1 ◽  
Ghuson. H.Mohammed2
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Zinc Oxide ◽  
Electrical Properties ◽  
Laser Pulse ◽  
Silicon Dioxide ◽  
Room Temperature ◽  
Pulsed Laser ◽  
Zno Thin Films ◽  
Pulse Deposition

In this paper zinc oxide was dopped by various concentrations (5,10,15,20,25) % of silicon dioxide. The mixture was deposited on glass substrate by laser pulse deposition at room temperature to obtain (Zn2SiO4) thin films. The D.C conductivity showed a decrease in activation energy by increasing doping from (Ea1=0.096 eV) to (Ea1=0.075 eV) before annealing and after annealing from (Ea1=0.048 eV) to(Ea1=0.027 eV). Hall effect showed that the concentration of carriers increases from (2.79 ×1018cm-3) to (14.29× 1018cm-3 ) before annealing and from (0.30×1016cm-3) to (26.25×1016cm-3) after annealing. The mobility decreases from(2.3cm2/v. sec) to (0.99cm2/v. sec) before annealing and from (7cm2/v. sec) to (2.5cm2/v . sec).   http://dx.doi.org/10.25130/tjps.23.2018.173  

scholarly journals Semiconducting properties of nonstoichiometric TiO2-x ceramics

2012 ◽  
Vol 6 (2) ◽  
pp. 91-95 ◽  
Author(s):  
Agnese Pura ◽  
Kristaps Rubenis ◽  
Dmitrijs Stepanovs ◽  
Liga Berzina-Cimdina ◽  
Jurijs Ozolins
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
High Vacuum ◽  
Titanium Oxides ◽  
Atmospheric Conditions ◽  
Semiconducting Properties ◽  
Two Stages ◽  
Extrusion Technology

Ceramics containing titanium oxides were prepared using extrusion technology and thermal treatment in two stages: sintering at normal atmospheric conditions at 1000 and 1200?C and annealing in high vacuum conditions at 950 and 1150?C. Electrical properties such as thermopower and electrical conductivity of cylindrical specimens have been studied at temperature range from the room temperature up to 350?C. Activation energy of the process has been determined from conductivity curves. Obtained thermopower values are in the range from 68 up to 105 mV at temperature gradient between the hot and cold ends of the samples at 300?C, while activation energy values are from 0.03 to 1.16 eV.

Electrical Properties of n-GaN/p-SiC and n-AlGaN/p-SiC Heterojunction Diodes

2001 ◽  
Vol 693 ◽  
Author(s):  
B. Luo ◽  
J. Kim ◽  
R. Mehandru ◽  
F. Ren ◽  
K. P. Lee ◽  
...  
Keyword(s):  
Activation Energy ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Normal Type ◽  
Defect States ◽  
Dark Line ◽  
Continuous States ◽  
Line Defects ◽  
Heterojunction Diodes

AbstractProperties of n-GaN/p-SiC and n-AlGaN/p-SiC heterojunctions prepared by HVPE on 4H SiC substrates were studied by means of C-V, C/G-T, C-f, I-V and DLTS. It is shown, in agrrement with earlier publications, that the GaN/p-SiC HJ is staggered type II with ΔEc=-0.4 eV andΔEv=0.6 eV. Whenchanging GaN for AlGaN with Al mole fraction of x=0.25-0.3 the band alignment becomes normal type I with ΔEc=0.2 eV andΔEv=0.6 eV. I-V characteristics of both heterojunctions bear evidence of strong tunneling via defect states, particularly centers with activation energy of 1.25 eV for GaN/4H SiC HJ. The tunneling was found to be more pronounced in the AlGaN/SiC HJs even though these HJs showed no evidence of formation of dark line defects at the interface, in contrast to GaN/SiC. DLTS measurements on both types of HJs revealed the presence of broad bands whose behavior is indicative of these bands being related to continuous states in the gap, most likely near the nitride/carbide interface.

Reactively Curable Rubbers—I: Diene Elastomers with Pendant Isocyanate and/or Hydroxyl Functionality

1990 ◽  
Vol 63 (4) ◽  
pp. 582-598 ◽  
Author(s):  
Dane K. Parker ◽  
Howard A. Colvin ◽  
Arthur H. Weinstein ◽  
Sun-Lin Chen
Keyword(s):  
Zinc Oxide ◽  
Emulsion Polymerization ◽  
Reactivity Ratios ◽  
Type I ◽  
Type Ii ◽  
Active Hydrogen ◽  
Blocking Group ◽  
Rubber Industry ◽  
The Subject ◽  
Blocked Isocyanate

Abstract In conclusion, we have demonstrated that modified diene elastomers containing active hydrogens and/or blocked-isocyanate derivatives can be crosslinked (cured) by three distinct methods. These methods include: 1. reaction of polymer-bound active hydrogens with monomeric polyisocyanates (Type I), 2. reaction of polymer-bound isocyanates with compounds containing two or more active hydrogens (Type II), and 3. reaction between polymer segments that contain both polymer-bound isocyanates and active hydrogens (Type III). Additionally, we have shown that the new polymerizable blocked-isocyanate derivatives (Type II and III systems) can be readily incorporated into SBR and NBR elastomers by standard emulsion-polymerization techniques. The degree and distribution of these monomers within the elastomer matrix were shown to be controlled by knowledge of their reactivity ratios. Furthermore, we have shown that the processing and properties of these systems can be readily controlled by the proper combination of isocyanate blocking group, active-hydrogen component, and catalyst. In many cases, these modified elastomers can be coagulated, dried, compounded, and cured using methods common to the rubber industry. Although not optimized, we have also shown that useful vulcanizates can be produced from extremely simple recipes. Conventional acceleration systems e.g., sulfur, accelerator, zinc oxide, are eliminated. The resulting urethane or urea crosslinks are remarkably durable under both thermal and hydrolytic conditions. Obviously, the possibilities for these uniquely reactive elastomers have not been exhausted. Many other intriguing applications of this technology are currently being explored. These applications will be the subject of future publications.

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