Dominant Ion Research Articles

Fragment ions produced from hexamethyldisilane in a Freeman-type ion source

Fragment ions produced from hexamethyldisilane (HMDS) in a Freeman-type ion source with a hot tungsten wire were studied using a low-energy mass analyzed ion beam system. Dominant fragment ions from HMDS were identified to be H+, H2+, C+, CH3+, Si+, SiCH4+, SiC2H6+, and SiC3H9+. The rates of ion fragment production strongly depended on the tungsten temperature. We conclude that the irradiation of the mass-selected SiCH4+ ions obtained from HMDS to Si substrates is useful for the secure epitaxial growth of SiC.

Correlation between dry etching resistance of Ta masks and the oxidation states of the surface oxide layers

Mechanisms of dry etching resistance of Ta masks, which are widely used for magnetic random access memory etching processes, have been investigated for a better understanding of their faceting characteristics. In magnetic-material etching processes by CO/NH3 or CH3OH plasmas, CO+ ion is considered as one of the most dominant ion species irradiating the substrate surface. An earlier study by Li et al. [J. Vac. Sci. Technol. A 33, 040602 (2015)] has shown that the Ta sputtering yield by CO+ ion irradiation depends strongly on the ion irradiation angle and the level of the surface oxidation. In this study, the primary focus is placed on the effects of surface oxidation and physical sputtering only (without possible chemical effects of carbon) on the etching rate of Ta, and the etching characteristics of Ta and Ta2O5 have been examined with Ar+ and/or oxygen ion beams. It has been found that there is a strong negative correlation between the etching rate of Ta and the oxidation states of the surface oxide layer formed during the etching process; the higher the oxidation states are, the lower the etching rate becomes. The results indicate that a strong propensity of a Ta mask to taper by irradiation of oxidizing ions (i.e., strong ion-irradiation-angle dependence of the Ta etching rate) arises from less efficient oxidation of a tapered surface by incident oxidizing ions, which enter the surface with an oblique angle.

Self-Consistent Model of a High-Power Hall Thruster Plume

A new model of the plasma plume from Hall effect thrusters (HETs) has been developed for the purpose of more accurately predicting the interactions between future high-power thrusters and large high-voltage solar arrays, such as those being developed under NASA’s Game Changing Technology awards by ATK and Deployable Space Systems. The HET plume mainly consists of two types of ions. The first are the energetic main beam ions produced upstream of the thruster acceleration zone. These are the dominant ion species along the thrust axis. The other group of ions have lower kinetic energy and are generated downstream of the acceleration zone from neutral xenon gas atoms by charge exchange (CEX) with main beam ions and by electron impact ionization. The neutral gas is due to neutral propellant atoms leaving the thruster and the hollow cathode without being ionized, and, in the case of laboratory testing, background neutrals present in the vacuum chamber. The new model uses the 2-D axisymmetric Hall thruster code, Hall2De, to self-consistently calculate the three major components of the plume in the vicinity of the thruster, which are the neutral gas atoms, high-energy beam ions, and low-energy ions. From the boundary computational region in the near plume, the Hall2De results are propagated to distances of tens of meters using a continuum hydrodynamic algorithm. This approach offers important advantages with respect to prior models of Hall thruster plumes, such as the NASA Electric Propulsion Interactions Code (EPIC), which uses an analytical fit to laboratory data from a single thruster for the main beam velocity boundary conditions at the channel exit. EPIC assumes that the neutral gas density emanates uniformly and isotropically from the channel exit. Low-energy ions are generated only by CEX; low-energy ions generated by electron impact are not included. The results for the far-field plume of a conceptual high-power thruster (H6) show important differences between EPIC and simulations using the new plume model. High-energy ions undergo less expansion in the azimuthal direction than in EPIC. This can be attributed to magnetic focusing of the beam. We also observe that the peak in low-energy ion density at approximately 90° from the thrust axis predicted by EPIC is moved downstream to angles from 70° to 80° when the new plume model is employed.

Water quality of the Helvetian and Eocene aquifers in Al Zerba catchment and southern parts of Al Qweek Valley, Aleppo basin, Syria

Groundwater is a key factor for sustainable socio-economic development in arid and semi-arid countries. The study area constitutes the south and southwestern parts of Aleppo basin, north of Syria. It is characterized by semi-arid climate and limited water resources. The aims of this study are to evaluate the groundwater quality with concern to drinking and irrigation suitability, water–rock interaction, and potential source rock to assess the main hydrochemical processes controlling chemical composition of groundwater in the Neogene and Paleogene aquifer systems. Hydrochemical data of 29 irrigation and observation wells distributed in the region were used in this study. Concentrations of the dominant ions are following the order Na+ > Ca2+ > Mg2+ > K+ and HCO3 − > Cl− > SO4 2− for major cations and anions, respectively. Ca–Na–HCO3, Na–Ca–SO4, and Ca–Na–Cl are the main groundwater types in the region. The graphical interpretation and cluster analysis of groundwater samples identified three main hydrochemical facies in the region. These groups are differentiated by three levels of total dissolved solids (TDS) value ranges from 390 mg/l for the group A, 742 and 1795 mg/l for the group B and C, respectively. The results also show that most of the groundwater samples are close to saturation or oversaturation with respect to the minerals: aragonite, calcite, and dolomite, while halite and gypsum are always under-saturated. Furthermore, the inverse geochemical modeling of groundwater samples indicates three main processes that are responsible for groundwater evolution in the region: plagioclase weathering (albite, hypersthene), de-dolomitization, and cation exchange. These processes increase in groundwater salinity from the east to the southwestern parts of the study area. The groundwater in the region is partly critical for drinking and irrigation due to the high average TDS (925 mg/l), nitrate (43.78 mg/l), and salinity. However, groundwater samples exhibited low sodium adsorption ratios, moderate magnesium hazard, and low residual sodium carbonate. Despite of that, this type of water can adversely affect the soil and crops yields in the long term and prevent a sustainable development of agriculture in the region of interest.

Characterization and Modeling of the Collision Induced Dissociation Patterns of Deprotonated Glycosphingolipids: Cleavage of the Glycosidic Bond.

Glycosphingolipid fragmentation behavior was investigated by combining results from analysis of a series of negative ion tandem mass spectra and molecular modeling. Fragmentation patterns extracted from 75 tandem mass spectra of mainly acidic glycosphingolipid species (gangliosides) suggest prominent cleavage of the glycosidic bonds with retention of the glycosidic oxygen atom by the species formed from the reducing end (B and Y ion formation). Dominant product ions arise from dissociation of sialic acids glycosidic bonds whereas product ions resulting from cleavage of other glycosidic bonds are less abundant. Potential energy surfaces and unimolecular reaction rates of several low-energy fragmentation pathways leading to cleavage of glycosidic bonds were estimated in order to explain observed dissociation patterns. Glycosidic bond cleavage in both neutral (unsubstituted glycosyl group) and acidic glycosphingolipids was the outcome of the charge-directed intramolecular nucleophilic substitution (SN2) mechanism. According to the suggested mechanism, the nucleophile in a form of carboxylate or oxyanion attacks the carbon at position one of the sugar ring, simultaneously breaking the glycosidic bond and yielding an epoxide. For gangliosides, unimolecular reaction rates suggest that dominant product ions related to the cleavage of sialic acid glycosidic bonds are formed via direct dissociation channels. On the other hand, low abundant product ions related to the dissociation of other glycosidic bonds are more likely to be the result of sequential dissociation. Although results from this study mainly contribute to the understanding of glycosphingolipid fragmentation chemistry, some mechanistic findings regarding cleavage of the glycosidic bond may be applicable to other glycoconjugates.

The relative proportions of water group ions in Saturn's inner magnetosphere: A preliminary study

AbstractWe present a technique to gather ion composition information in the form of relative abundances of the water group ion species in Saturn's inner magnetosphere, utilizing the Cassini Plasma Spectrometer's Straight‐Through Time‐of‐Flight data from two orbits in 2011. We show that between 4.75 and 8 Saturn radii H2O+ ions dominate the water group species, and from 8 to 10 Saturn radii it is OH+ ions that dominate. Our results show that the relative proportion of H3O+ falls fastest with increasing distance, while the proportion of H2O+ decreases slowly. However, O+ and OH+ increase with distance, and O+ is the least dominant ion species out to eight Saturn radii outside of which it is comparable to H3O+. The relative abundance of H2O+ found here matches theoretical work based on Herschel telescopic data very well. These results are compared with other published work, and further improvements to the technique are discussed.

Water-soluble ions in atmospheric aerosols measured in five sites in the Yangtze River Delta, China: Size-fractionated, seasonal variations and sources

Abstract In order to investigate the regional variations of water-soluble ions (WSIs), size-resolved measurement of aerosol particles and WSIs was conducted by using Anderson Sampler and Ion Chromatography at five sites (Nanjing, Suzhou, Lin'an, Hangzhou and Ningbo) in the Yangtze River Delta (YRD) region, China in the Autumn of 2012 and Winter, Spring and Summer of 2013. WSIs exhibited obvious seasonal variations due to the monsoon conversion, with the highest level in winter and lowest level in summer. The aerosol mass concentrations and WSIs in different size segments varied with four seasons. The dominant ions concentrations in PM2.1 ranked in the order of SO 4 2 − > NO 3 − > NH 4 + > Cl− > K+ > Ca2+, and the dominant ions concentrations in PM2.1–10 ranked in the order of Ca2+ > NO 3 − > SO 4 2 − > Cl− > NH 4 + > Na+. The size spectra of mass and WSIs concentration peaked mostly at 0.43–0.65 μm in four seasons. The concentration discrepancies of WSIs in different cities were caused by the geographic locations and emission source. It's belonged to ammonium-rich distribution in PM2.1 and ammonium-poor distribution in PM2.1–10 in the YRD region. The impact of temperature on mass concentrations of NO 3 − and NH 4 + in PM2.1 were stronger than those in PM2.1−10. PCA analysis shows that the sources of WSIs dominant by anthropogenic sources, soil particles or falling dust, sea salt and burning process.

Groundwater Quality Investigation in Udayarpalayam Taluk, Ariyalur District, Tamilnadu, India

Ariyalur is one of the districts in Tamilnadu it is rich in limestone resource. A study on geochemical characterization of ground water and its suitability for drinking purposes was carried out. Twenty five groundwater samples were collected from bore wells and open wells during Pre monsoon seasons of 2014. Groundwater is the main principle source for drinking, irrigation water and other activities in our study area. It is an indispensable source of our life. The problem of groundwater quality obtains high importance in this present-day, whether in the study area or any other countries in the world. The present study was carried out to analyse and evaluate the groundwater samples collected from residential areas of Udayarpalyam Taluk. The analyzed physicochemical parameters such as pH, electrical conductivity, total dissolved solids, calcium, magnesium, sodium, potassium, bicarbonate, sulphate, phosphates, chloride, nitrate, and fluoride are used to characterize the groundwater quality and its suitability for drinking uses. Calcium, sodium, chloride and sulphate are the dominant ions in the groundwater chemistry. The Groundwater is not suitable for drinking purposes at several locations in this area. Each parameter was compared with its standard permissible limit as prescribed by WHO/BIS. The analytical results indicated that the ground water quality was found unsatisfactory for drinking purpose in some location.

Groundwater Quality Investigation in Udayarpalayam Taluk, Ariyalur District, Tamilnadu, India

Ariyalur is one of the districts in Tamilnadu it is rich in limestone resource. A study on geochemical characterization of ground water and its suitability for drinking purposes was carried out. Twenty five groundwater samples were collected from bore wells and open wells during Pre monsoon seasons of 2014. Groundwater is the main principle source for drinking, irrigation water and other activities in our study area. It is an indispensable source of our life. The problem of groundwater quality obtains high importance in this present-day, whether in the study area or any other countries in the world. The present study was carried out to analyse and evaluate the groundwater samples collected from residential areas of Udayarpalyam Taluk. The analyzed physicochemical parameters such as pH, electrical conductivity, total dissolved solids, calcium, magnesium, sodium, potassium, bicarbonate, sulphate, phosphates, chloride, nitrate, and fluoride are used to characterize the groundwater quality and its suitability for drinking uses. Calcium, sodium, chloride and sulphate are the dominant ions in the groundwater chemistry. The Groundwater is not suitable for drinking purposes at several locations in this area. Each parameter was compared with its standard permissible limit as prescribed by WHO/BIS. The analytical results indicated that the ground water quality was found unsatisfactory for drinking purpose in some location.

Residential wood combustion in two domestic devices: Relationship of different parameters throughout the combustion cycle

Logs of three common Southern and mid-European woods (Quercus pyrenaica, Populus nigra and Fagus sylvatica) were burned in two different combustion appliances, a fireplace and a stove. The flue gas composition was monitored continuously in the exhaust ducts of both burning appliances for total hydrocarbons (THC) and carbon oxides (CO2 and CO). Particulate matter with aerodynamic diameter below 2.5 μm (PM2.5) was sampled in a dilution tunnel under isokinetic conditions and chemically characterised for water soluble-inorganic ions, organic and elemental carbon and levoglucosan, mannosan, and galactosan. The evolution of the emission factors of these components throughout the combustion cycle was studied. The fireplace was the combustion appliance with the highest CO, CO2, THC and PM2.5 emission factors. The carbonaceous matter represented 72–84% of the particulate mass emitted, regardless of species burned and combustion devices. OC/EC ratios were higher for the fireplace than for the stove, and showed a significant potential relation with K+/levoglucosan. The dominant water soluble inorganic ions in smoke particles were K+, PO43−, SO42−, and Na+. Anhydrosugar emissions were strongly enhanced in the start-up phase, when lower temperatures are registered, and decreased progressively until the glowing combustion phase. However, K+ emission seems to be higher in flaming-dominated combustion at higher temperature. Statistical analyses, including the Kruskal–Wallis test, principal component analysis and Pearson correlation between emission factors, were carried out. A significant correlation between NH4+ and levoglucosan was found for both appliances.

Spatial profiles of potential, ion concentration and flux in short unipolar and bipolar nanopores

During release of vesicular content the resistance of the fusion pore sometimes changes rapidly and repeatedly. However, it is not clear why the pore ‘flickers’. Engineered nanopores often rectify, but how different factors influence the rectification requires clarification. To better understand the ionic ‘causes’ of pore conductivity and its changes we simulated ion transport through a short nanopore using Poisson–Nernst–Planck equations, coupling it to the transport of water using Navier–Stokes equations. We extracted the potential, concentration, and ion flux profiles. In uniformly charged nanopores the voltage bias determines which counter-ion flux dominates, and it is carried by the counter-ions of the highest concentration. In unipolar nanopores this simple rule breaks down. The dominant counter-ion in the charged half is from the adjacent compartment, but the bias determines what counter-ion flux is dominant — the same ion (regular bias), or a different and smaller (reverse bias), and this difference determines the level of rectification. In bipolar nanopores the dominant counter-ions in each half are from the adjacent compartments, and the total ion concentration dips in the middle near the wall. With regular bias the total ion concentration peaks in the pore center; the ions that carry the current through the nanopore start as counter-ions and their fluxes are large. With reverse bias the total concentration dips near the wall and in the center, both dominant ion fluxes through the nanopore start as co-ions and are very small, whereas those starting as counter-ions do not go through.

Comparison of surface water chemistry and weathering effects of two lake basins in the Changtang Nature Reserve, China

The geochemistry of natural waters in the Changtang Nature Reserve, northern Tibet, can help us understand the geology of catchments, and provide additional insight in surface processes that influence water chemistry such as rock weathering on the Qinghai–Tibet Plateau. However, severe natural conditions are responsible for a lack of scientific data for this area. This study represents the first investigation of the chemical composition of surface waters and weathering effects in two lake basins in the reserve (Lake Dogaicoring Qiangco and Lake Longwei Co). The results indicate that total dissolved solids (TDS) in the two lakes are significantly higher than in other gauged lakes on the Qinghai–Tibet Plateau, reaching 20–40g/L, and that TDS of the tectonic lake (Lake Dogaicoring Qiangco) is significantly higher than that of the barrier lake (Lake Longwei Co). Na+ and Cl− are the dominant ions in the lake waters as well as in the glacier-fed lake inflows, with chemical compositions mainly affected by halite weathering. In contrast, ion contents of inflowing rivers fed by nearby runoff are lower and concentrations of dominant ions are not significant. Evaporite, silicate, and carbonate weathering has relatively equal effects on these rivers. Due to their limited scope, small streams near the lakes are less affected by carbonate than by silicate weathering.

Influence of mixture compositions on ion energy distributions in Ar/N2 electron cyclotron resonance plasma

In this report, the mass and energy spectra of ions in Ar/N2 electron cyclotron resonance (ECR) plasma at the microwave power of 100 W and the gas pressure of 1 Pa are investigated by a Hiden EQP analyzer, and also the plasma optical emission spectra are recorded by optical emission spectroscopy (OES). Singly charged Ar+ and N2+ as the dominant ions are detected. The ion energy distribution functions (IEDFs) of Ar+ and N2+ exhibit complicated evolutions of peak structures with varying the N2 fractions. The IEDF of Ar+ is bimodal at the low N2 fractions, and changes to trimodal structure as the N2 fractions are near 40%. However, it turns to be unimodal at the N2 fractions above 80%. The IEDFs of N2+ present unimodal structures in the case of both high and low N2 fractions, and the bimodal profiles appear as the N2 fractions are around 50%. It is suggested that the distributed ionization and the charge–exchange reactions between ions and neutrals are responsible for the evolutions of peak structures for IEDFs.

The puzzling spectrum of HD 94509

The spectral features of HD 94509 are highly unusual, adding an extreme to the zoo of Be and shell stars. The shell dominates the spectrum, showing lines typical for spectral types mid-A to early-F, while the presence of a late/mid B-type central star is indicated by photospheric hydrogen line wings and helium lines. Numerous metallic absorption lines have broad wings but taper to narrow cores. They cannot be fit by Voigt profiles. We aim to describe and illustrate unusual spectral features of this star, and make rough calculations to estimate physical conditions and abundances in the shell. Furthermore, the central star is characterized. We assume mean conditions for the shell. An electron density estimate is made from the Inglis-Teller formula. Excitation temperatures and column densities for Fe I and Fe II are derived from curves of growth. The neutral H column density is estimated from high Paschen members. The column densities are compared with calculations made with the photoionization code Cloudy. Atmospheric parameters of the central star are constrained employing non-LTE spectrum synthesis. Overall chemical abundances are close to solar. Column densities of the dominant ions of several elements, as well as excitation temperatures and the mean electron density are well accounted for by a simple model. Several features, including the degree of ionization, are less well described. HD 94509 is a Be star with a stable shell, close to the terminal-age main sequence. The dynamical state of the shell and the unusually shaped, but symmetric line profiles, require a separate study.

Ion source development for ultratrace detection of uranium and thorium

Efficient ion sources are needed for detecting ultratrace U and Th impurities in a copper matrix by mass spectrometry techniques such as accelerator mass spectrometry (AMS). Two positive ion sources, a hot-cavity surface ionization source and a resonant ionization laser ion source, are evaluated in terms of ionization efficiencies for generating ion beams of U and Th. The performances of the ion sources are characterized using uranyl nitrate and thorium nitrate sample materials with sample sizes between 20 and 40μg of U or Th. For the surface ion source, the dominant ion beams observed are UO+ or ThO+ and ionization efficiencies of 2–4% have been obtained with W and Re cavities. With the laser ion source, three-step resonant photoionization of U atoms has been studied and only atomic U ions are observed. An ionization efficiency of about 9% has been demonstrated. The performances of both ion sources are expected to be further improved.

The consequences of disposing wastewater in an endorheic wetland in southwest Iran.

Wetlands are important ecosystems both at regional and global scales. They are home to a diverse group of flora and fauna, and provide water for drinking, irrigation, and recreational purposes. Miangaran endorheic wetland in SW Iran serves as the discharge point of the municipal wastewater of a nearby city; it receives agricultural return flows as well. To identify the consequences of the wastewater input, 29 water samples from the wetland's body and inlet streams were analyzed for physico-chemical parameters. The average EC of the wetland was 405 μS/cm; calcium, magnesium, and bicarbonate were the dominant ions. The average pH was high, about 8.6, due to carbonate dissolution in the drainage area which was exacerbated by photosynthesis process inside the wetland. The concentration of phosphate was over the eutrophication limit of 0.1 mg/L. Nitrate contents varied from 5.7 to 12.3 mg/L. Trophic state index based on total nitrogen was about 63, falling within the eutrophic group. Heavy metal concentrations were generally higher than WHO drinking limits. Highest values of EC, nutrients, and metals were observed in the south and northwest, clearly signifying the role of wastewater input as the main source of contamination, which has resulted in the eutrophication of the wetland.

Numerical modeling of the effect of the level of nitrogen impurities in a helium parallel plate dielectric barrier discharge

In this paper a validated 2D axisymmetric plasma fluid model was used to study the influence of the level of nitrogen impurities on the processes that occur in a helium parallel plate dielectric barrier discharge. The level of nitrogen impurities was varied in the range 0.1–500 ppm. It was observed that the nitrogen impurities significantly affect the dominant ion species at breakdown and the discharge characteristics. Specifically, three different dominant ions were found, which are strongly dependent on the level of nitrogen impurities. These are: (0.1–35 ppm), (35–150 ppm) and (150–500 ppm). In addition, the results show that the discharge characteristics are dependent on the dominant ion species at breakdown.

Hydrochemistry and its controlling factors of rivers in the source region of the Yangtze River on the Tibetan Plateau

This study focuses on the chemical composition, and the factors controlling it, of the high mountain-rivers in the source region of the Yangtze River on the Tibetan Plateau. By comprehensive and systematic analysis, the chemical signatures, spatial variations of water quality, as well as the factors controlling them are studied. The value of the average total dissolved solids (TDS) is 778mg/l, ranging from 117 to 5496mg/l. In order of decreasing concentration, the main cations are Na+, Ca2+, Mg2+, and K+, while the main anions are Cl−, HCO3−, SO42−, and NO3−. Na+ and Cl− are the dominant ions, accounting for 74.2% and 63.7% of the total cations and anions, respectively, followed by Ca2+ and HCO3−, which account for 14.3% and 25%, respectively. The Piper diagram shows the main water type to be a Cl−·HCO3−–Na+·Ca2+ type. From the Gibbs boomerang model, we conclude that the chemistry of the river water is controlled by lithogenic weathering processes. The Na-normalized ratio end-member diagram indicates that the weathering of silicates and carbonates is relatively significant, on the whole. There exists pronounced regional heterogeneity in the water chemistry and the factors affecting it. The northern rivers, including Chumaer He, Beilu He, and Ranchiqu, are mainly affected by evaporation and crystallization processes, while the southern rivers (Tuotuo He, Gaerqu, and Buqu) show effects from the weathering of carbonates and silicates.

Spatial-temporal patterns of major ion chemistry and its controlling factors in the Manasarovar Basin, Tibet

The Manasarovar Basin in southern Tibet, which is considered a holy land in Buddhism, has drawn international academic attention because of its unique geographical environment. In this study, based on actual measurements of major ion concentrations in 43 water samples collected during the years 2005 and 2012, we analyzed systemically the spatial-temporal patterns of water chemistry and its controlling factors in the lake and inflowing rivers. The results reveal that the water in the Manasarovar Basin is slightly alkaline, with a pH ranging between 7.4–7.9. The amounts of total dissolved solids (TDS) in lake and river waters are approximately 325.4 and 88.7 mg/l, respectively, lower than that in most of the surface waters in the Tibetan Plateau. Because of the long-term effect of evaporative crystallization, in the lake, Na+ and HCO3 − have the highest concentrations, accounting for 46.8% and 86.8% of the total cation and anion content. However, in the inflowing rivers, the dominant ions are Ca2+ and HCO3 −, accounting for 59.6% and 75.4% of the total cation and anion content. The water exchange is insufficient for such a large lake, resulting in a remarkable spatial variation of ion composition. There are several large inflowing rivers on the north side of the lake, in which the ion concentrations are significantly higher than that on the other side of the lake, with a TDS of 468.9 and 254.9 mg/l, respectively. Under the influence of complicated surroundings, the spatial variations in water chemistry are even more significant in the rivers, with upstreams exhibiting a higher ionic content. The molar ratio between (Ca2++Mg2+) and (Na++K+) is much higher than 1.0, revealing that the main source of ions in the waters is carbonate weathering. Although natural processes, such as rock weathering, are the major factors controlling main ion chemistry in the basin, in the future we need to pay more attention to the anthropogenic influence.

An analytic approach to the degradation of double-Schottky barrier: Theoretical prediction of VO0–Zni2+:Zni2+ as dominant mobile ion in ZnO electroceramic

An analytic approach, aimed at characterizing the degradation properties of the double-Schottky barrier formed at the grain boundary in various electroceramics, is exhaustively described. Migration and neutralization behavior of charged defect ions is portrayed during the degradation of electrostatic potential under electrical stress. By comparing simulation results with experimental data from the aging test performed on fabricated [0 0 0 1] ZnO bicrystals, Zni2+ from VO0–Zni2+ complex donor defect is identified as the optimum candidate for the mobile ion responsible for degradation phenomena of ZnO electroceramics.