Importance of oxygen atmosphere to recover the ZnO-based varistors properties

Ramírez, M. A.; Simões, Alexandre Zirpoli; Bueno, Paulo Roberto; Márquez, María del Carmen Bellido; Orlandi, Marcelo Ornaghi; Varela, José Arana

doi:10.1007/s10853-006-0589-3

Cited by 42 publications

(39 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Summarized Degradation Mechanism Eda et al [16][17][18] ion migration process Takahashi et al 19 chemical desorption of oxygen ions at the grain boundaries Chiang et al 20 asymmetrical distribution of impurity ions in grain boundary region Sato et al 21,22 electrons captured by traps inside depletion layer and thus accumulated near grain boundary Gupta et al 15 migration process of zinc interstitial (the seminal grain-boundary defect model) Sonder et al 23 high mobility of oxygen ion at high temperature, and flaws like micro-cracks in varistor act as conduits for oxygen Bui et al 24 partial discharges causing the formation of HNO 3 that degrades the Schottky barrier Ramírez et al 25 the lost of oxygen species and β-Bi 2 O 3 phase during degradation process leading to abnormal degradation phenomena and determining its degradation rate, 26 whereas knowledge from atomic scale is quite limited on the role of element that is individually doped and, worse, on the co-doping effect.…”

Section: Researchersmentioning

confidence: 99%

Electrical degradation of double-Schottky barrier in ZnO varistors

Cheng

2016

AIP Advances

View full text Add to dashboard Cite

Researches on electrical degradation of double-Schottky barrier in ZnO varistors are reviewed, aimed at the constitution of a full picture of universal degradation mechanism within the perspective of defect. Recent advances in study of ZnO materials by atomic-scale first-principles calculations are partly included and discussed, which brings to our attention distinct cognition on the native point defects and their profound impact on degradation.

show abstract

Section: Researchersmentioning

confidence: 99%

Electrical degradation of double-Schottky barrier in ZnO varistors

Cheng

2016

AIP Advances

View full text Add to dashboard Cite

show abstract

“…10,11 Also, it has been shown that degraded ZnO varistors can recover their properties under an oxygen atmosphere. 12 These type of experiments can be explained as the result of the deformation of Schottky barriers present in the grain boundaries in which oxygen vacancies play a central role. [13][14][15][16][17][18] In this work, thick films of SnO 2 were made using the screen-printing method onto alumina substrates on which electrodes with an interdigitated shape were deposited by sputtering.…”

Section: Introductionmentioning

confidence: 99%

Study of the oxygen vacancies changes in SnO2 polycrystalline thick films using impedance and photoemission spectroscopies

Schipani

Ponce

Joanni

et al. 2014

Journal of Applied Physics

View full text Add to dashboard Cite

Studies of ambient dependent electrical behavior of nanocrystalline SnO 2 thin films using impedance spectroscopy J. Appl. Phys. 87, 7457 (2000); 10.1063/1.373010Dependence of indium-tin-oxide work function on surface cleaning method as studied by ultraviolet and x-ray photoemission spectroscopies J. Appl. Phys. 87, 295 (2000); 10.1063/1.371859Photoemission study of the interface between phenyl diamine and treated indium-tin-oxide Appl. Phys. Lett. 75, 1357Lett. 75, (1999 Changes in the concentration of oxygen vacancies within the grains of polycrystalline SnO 2 , due to different atmosphere exposures, were detected using impedance and photoemission spectroscopies. From measured capacitance values, variations of the potential barrier widths could be determined. It is shown that under the presence of an oxygen rich atmosphere, at relatively low temperature, the width of intergranular potential barriers increase to the point that grains become completely depleted of carriers. With subsequent exposure to vacuum, capacitance adopts a higher value, indicative of intergranular barriers and quasi-neutral regions at the center of the grains. X-ray and ultraviolet photoemission spectroscopy measurements showed that SnO 2 samples treated in oxidizing or reducing environments have similar barrier heights and different work functions. Results are especially relevant in the study of mechanisms responsible for metal oxide gas sensing. V C 2014 AIP Publishing LLC.[http://dx

show abstract

“…This aspect should be carefully evaluated. In ZnO.Bi 2 O 3 -based varistor systems, changes also occur in both phases, the amorphous and crystalline phase of Bi 2 O 3 during the processing or its useful life 7,20 . The varistors submitted to different stresses during use can modify its crystalline structure, which can cause the degradation process 7 .…”

Section: Resultsmentioning

confidence: 99%

Microstructural and nonohmic properties of ZnO.Pr6O11 CoO polycrystalline system

et al. 2010

View full text Add to dashboard Cite

the effective cross-section area of the elements is increased 14 . Several studies describe the dependence of varistor properties on processing conditions of Pr-doped ZnO varistors, especially in the field of grain boundary formation [2][3][4] 13 . It is very important to understand the structure, composition and properties of the boundaries since they have a strong influence on electrical properties. Our purpose is to investigate the microstructure, the current density-electric field (J vs. E) characteristics, and the capacitance-voltage (C-V) characteristics of ZPC varistor systems. Experimental ProcedureThe varistor systems (95-x) mol% ZnO + x mol% Pr 6 O 11 + 5 mol% CoO (x = 0.1, 0.5 and 1.0) were prepared from the mixture of oxide precursors method, all of them being analytical grade oxides: ZnO (Aldrich-99.99%), Pr 6 O 11 (Aldrich-99.9%) and CoO (Riedel-99.9%). The starting materials were attrition-milled in water for 3 hours. Then the dry slurry was calcined at 750 °C in air for 2 hours. The calcined powders were pulverized using agate mortar and pestle and after 2 wt. (%) polyvinyl alcohol (PVA) binder addition, granulated by sieving 200-mesh screen to produce the starting powder. The powder was uniaxially pressed into discs of 12 mm diameter and 1 mm thickness at a pressure of 80 MPa. The pellets were sintered at 1300 and 1350 °C for 2 hours with a heating rate of 5 °C/min followed by furnace cooling. The samples were characterized by X-ray diffraction (XRD, Rigaku, 20-2000), 40 kV and 150 mA from 2θ (20 to 80°), ∆2θ = 0.02°, with Cukα wavelength monocromatized by a graphite crystal. To obtain the Scanning Electron Microscopy (SEM) micrographies (ZEISS ® DSM 940 A) the sintered samples were polished and thermally etched by heating at 100 °C below the IntroductionZnO varistor ceramics are resistor devices manufactured by sintering ZnO powder containing various minor additives 1 . It has been recognized that at least two different classes of additives must be added to the ceramic varistors in order to obtain good nonohmic characteristics 2 . The first class of such additives are varistor-forming oxides (VFO), such as Bi 2 O 3 , Pr 6 O 11 , La 2 O 3 , BaO, V 2 O 5 and glass frits. The second class of additives are 3d transition-metal oxides, which improve significantly the nonohmic characteristics 3 . Zinc oxide ceramics, containing Pr 6 O 11 and CoO, which exhibit current nonohmic characteristics, were first reported by Mukae et al. 4 . In fact, the history of Pr 6 O 11 -based ZnO varistors is similar to the Bi 2 O 3 -based ZnO varistors 5 , but they have not been adequately studied. However, the Pr 6 O 11 -based ZnO varistors don't have volatilization of components 3 and they own a simpler microstructure when compared with Bi 2 O 3 -based varistors, which is an important fact for the stability and degradation phenomena [6][7][8][9] . Most of commercial ZnO varistors are ZnO-Bi 2 O 3 -based varistor ceramics, possessing as major additive Bi 2 O 3 . Although they exhibit excellent varistor perform...

show abstract

Importance of oxygen atmosphere to recover the ZnO-based varistors properties

Cited by 42 publications

References 15 publications

Electrical degradation of double-Schottky barrier in ZnO varistors

Electrical degradation of double-Schottky barrier in ZnO varistors

Study of the oxygen vacancies changes in SnO2 polycrystalline thick films using impedance and photoemission spectroscopies

Microstructural and nonohmic properties of ZnO.Pr6O11 CoO polycrystalline system

Contact Info

Product

Resources

About