Surface conductivity produced on zinc oxide by zinc and hydrogen

Thomas, D. G.; Lander, J. J.

doi:10.1016/0022-3697(57)90077-x

Cited by 30 publications

(4 citation statements)

References 8 publications

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“…The second sharp and strong endothermic peak located at 258 ~ corresponds to the formation of ZnO. The third exothermic peak located at 578 ~ may be related to the dissociation of ZnO into interstitial Zn metal [14,15]. The influences of iron ion additions on the decomposition processes of BZC are shown if Fig.1.…”

Section: Resultsmentioning

confidence: 95%

Influence of iron ion additions on the thermal decomposition of basic zinc carbonate

Said

Hassan

El-Salaam

et al. 1990

Journal of Thermal Analysis

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Thermal decomposition of pure basic zinc carbonate (BZC) and doped or mixed with iron ions were studied using TG, DTA and kinetics of isothermal decomposition. The TG and DTA investigations revealed that, the presence of iron ions retards the decomposition processes of (BZC). Also, the retardation effect increases on increasing of iron concentration up to 50 at.%. The curves of isothermal decomposition show the usual sigmoidal character. The decomposition velocity eontsant (K) values are plotted vs. liT according to Arrhenius equation gave a plot of good straight lines with activation energies of 43.7, 48.2, 53.2 and 57.1 kJ mo1-1 for pure (BZC) and incorporated with 1, 10, 30 and 50 at.% Fe 2+ respectively. The products of the thermal decomposition of pure BZC and mixed with iron ions are characterized using X-ray diffraction, IR spectroscopy, surface area determination and the surface porosity. These investigations showed that iron ions are effectively incorporated into zinc oxide lattice in the range of 30-50 at.%, which gave a ZnFe204 spinel.Mixed oxides, especially binary system, have been employed sucessfuUy in many industrial catalytic processes [1,2]. The combination of two transition metal oxides may affect their stoiehiometry and their surface, electrical, catalytic and thermal properties [3][4][5]. It was observed that the presence of foreign ion in the host lattice of solids markedly influences the reaction rate of solid-phase reaction [6]. This fact has been attributed to the change in the defect structure of reacting substances [7,8]. On addition it was found that [9,10], the active sites as well as the electronic structure of the semiconductor surface are changed in the presence of foreign cations.

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Section: Resultsmentioning

confidence: 95%

Influence of iron ion additions on the thermal decomposition of basic zinc carbonate

Said

Hassan

El-Salaam

et al. 1990

Journal of Thermal Analysis

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“…In addition, there 58 are additional reports of resistivity degradation of ZnO varistors 59 due to hydrogen gas exposure [11,13]. It will be shown in this 60 report that the leakage current can increase from 10 À8 to 10 À4 A 61 at 170°C after one hour exposure to hydrogen gas.…”

mentioning

confidence: 86%

“…The source of hydrogen 46 gas could, for example, be the out-gassing of corrosive atmo-47 spheres from incompletely cured epoxies and or electrolytic capac-48 itor seal failure [9][10][11]. 49 There have been earlier studies on the atmosphere sensitivity to 50 varistors, such as the work of Sonder et al [12] [11,13]. It will be shown in this 60 report that the leakage current can increase from 10 À8 to 10 À4 A 61 at 170°C after one hour exposure to hydrogen gas.…”

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confidence: 98%

Evaluation of Atomic Layer Deposition coating as gas barrier against hydrogen gas and humidity

Heidary

Randall

2015

Scripta Materialia

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a b s t r a c t 25 Effectiveness of HfO 2 Atomic Layer Deposition coatings has been studied on ZnO varistors by I-V tests, 26 impedance spectroscopy, and highly accelerated life test. Based on impedance spectroscopy analyses, 27 the proton diffusion coefficient was measured to be 400 K times less in the coating. Transmission electron 28 microscopy analysis shows that Atomic Layer Deposition films are continuous and conformal. After expo-29 sure to high temperature, partial crystallization was detected in the coating and increases proton diffu-30 sion coefficient by 150 times. 31 32 33 34 35 Varistors or variable resistors are passive components, 36 which are used in protection against voltage surges, that shunt 37 the excess charge to the ground [1-4]. The design is typically 38 around ceramic materials based on ZnO with dopants and sintering 39 aids added to control the nature of the controlled breakdown pro-40 cess and minimize the leakage in the stand-by operational condi-41 tion [4,5]. The grain size and the grain boundary compositions 42 are critical and are back-to-back Schottky barriers controlling 43 these conditions [6,7,1,3]. There is concern about the packaging 44 of varistor components at the atmosphere in which they are 45 exposed to humidity or hydrogen gas [8]. The source of hydrogen 46 gas could, for example, be the out-gassing of corrosive atmo-47 spheres from incompletely cured epoxies and or electrolytic capac-48 itor seal failure [9-11]. 49 There have been earlier studies on the atmosphere sensitivity to 50 varistors, such as the work of Sonder et al. [12] who have studied 51 systematically the effects of reducing atmosphere on the resistivity 52 degradation of ZnO varistors. In their case, a reductive agent of CO 53 and different percentage of oxygen and inert gas at the interval 54 temperature of 150-800°C were considered. It was found that 55ZnO varistors can be degraded by annealing at 260°C in a 56 CO/CO 2 atmosphere, and showing resistance can decrease from 57 10 10 to 10 4 X after 33 h of exposure to CO/CO 2 . In addition, there 58 are additional reports of resistivity degradation of ZnO varistors 59 due to hydrogen gas exposure [11,13]. It will be shown in this 60 report that the leakage current can increase from 10 À8 to 10 À4 A 61 at 170°C after one hour exposure to hydrogen gas. 62 ALD (Atomic Layer Deposition) coatings demonstrate a good gas 63 barrier property [14-17] on various substrates, which makes them 64 promising to hinder the degradation process. In this letter, the 65 effect of exposure of ZnO varistors to forming gas (4% hydrogen 66 and 96% nitrogen) and humidity has been studied, and the applica-67 tion of ALD coating as a gas barrier layer has been evaluated. In 68 addition, the proton diffusion coefficient has been measured for 69 both ZnO varistor and HfO 2 ALD layers to demonstrate effective-70 ness as gas and humidity barriers for ZnO based varistors. 71 A commercial ZnO varistor was cut to 15 Â 15 Â 1.4 mm and 72 ground up to 1200 grit sandpaper, then a circula...

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“…The adsorption of zinc vapour results also in a comparable saturation value of surface conductivity. 41 In connection with these results the well-known investigations of the hydrogen adsorption on ZnO by Taylor and his co-workers 17 are very interesting.…”

Section: Influence Of Adsorbed Gases On the Surface Conductivity Oxyg...mentioning

confidence: 81%

Surface conductivity of semiconductors and its variation by adsorption, transverse electric fields and irradiation

Heiland¹

1959

Discuss. Faraday Soc.

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The surface of semiconductors is covered with a space-charge layer, which is caused by intrinsic or adsorbed donors and acceptors. Also chemical reaction and diffusion of defects can produce a surface layer whose conductivity differs greatly from the bulk value. Examples are given for zinc oxide and germanium with oxygen and hydrogen.Information on the energy levels for electrons at the surface can be gathered from systematic variations of the surface conductivity. With zinc oxide three such experiments have been carried out : field effect (change of carrier density at the surface due to transverse electric fields), adsorption of oxygen, and irradiation with light or electrons. The results are given as drift mobilities of electrons. A consistent explanation is possible with a surface model containing a set of continuously distributed surface states just below the conduction band.Closely connected with the surface photoconductivity are photodesorption and photolysis. Not only electron transitions but also ion migrations are involved in these cases. examples are given for zinc oxide and the sulphides of zinc and cadmium.

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Surface conductivity produced on zinc oxide by zinc and hydrogen

Cited by 30 publications

References 8 publications

Influence of iron ion additions on the thermal decomposition of basic zinc carbonate

Influence of iron ion additions on the thermal decomposition of basic zinc carbonate

Evaluation of Atomic Layer Deposition coating as gas barrier against hydrogen gas and humidity

Surface conductivity of semiconductors and its variation by adsorption, transverse electric fields and irradiation

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