Conduction mechanism and defect density of states in amorphous Te15 (Se100-xBix)85 glassy alloys

189-192The present paper reports the dc conductivity measurement up to 100 V for pallets of Te15 (Se100-xBix)85 (x=0, 1, 2, 3, 4 at %) glassy alloys in temperature range (303-343 K). The dc conductivity is calculated from the I-V characteristics curves of the pellets of bulk samples prepared by melt quenching technique. The samples obey Ohm’s law in the lower (0-25 V) voltage range whereas the behaviour in the higher (25-100 V) voltage range is non-ohmic. The experimental results for all the samples fit well with the theory of space charge limited conduction SCLC for uniform distribution of localized states in the mobility gap. The density of defect states is calculated for the glassy alloys and is found to increase with Bi content. The increase in defect density of states can be explained on basis of electro negativity difference of Bi as compared to host elements. The increase in dc conductivity is probably due to Se-Bi bond concentration in the Se-Te-Bi glasses

Conduction mechanism and defect density of states in amorphous Te15 (Se100-xBix)85 glassy alloys

The present paper reports the dc conductivity measurement up to 100 V for pallets of Te15 (Se100-xBix)85 (x=0, 1, 2, 3, 4 at %) glassy alloys in temperature range (303-343 K). The dc conductivity is calculated from the I-V characteristics curves of the pellets of bulk samples prepared by melt quenching technique. The samples obey Ohm’s law in the lower (0-25 V) voltage range whereas the behaviour in the higher (25-100 V) voltage range is non-ohmic. The experimental results for all the samples fit well with the theory of space charge limited conduction SCLC for uniform distribution of localized states in the mobility gap. The density of defect states is calculated for the glassy alloys and is found to increase with Bi content. The increase in defect density of states can be explained on basis of electro negativity difference of Bi as compared to host elements. The increase in dc conductivity is probably due to Se-Bi bond concentration in the Se-Te-Bi glasses

Structural analysis and theoretical investigations in Pb additive Se-Te-Ge chalcogenide nano-composites

In the present study, the impact of lead addition on the structural and physical properties of newly prepared quaternary (Se80Te20)94-xGe6Pbx (x= 0, 2, 4, 6, 8 and 10) chalcogenide nano-composites has been studied in detail. Nano particle size of each Pb addtive chalcogenide alloy has been deduced using the highest intensity peak of the X-ray diffractograms and it has also been confirmed by field emission scanning electron microscope (FESEM). The detailed study of physical parameters namely average co-ordination number (Z) and number of constraints, lone pair electrons, glass transition temperature, heat of atomization, cohesive energy and energy gap has been made. It is observed that Z and constraints have been found to increase with the addition in Pb content. However, all the other investigated parameters viz lone pair electrons, glass transition temperature, heat of atomization, cohesive energy and energy gap show a reverse variation. Glass transition temperature has been estimated theoretically using Tichy-Ticha approach and found to be in consonance with the experimental results. The cohesive energy has been calculated using chemical bond approach (CBA) model. Due to lower band gap of Pb, the overall bandgap of the composition has been found to decrease with Pb at.wt.%

Non-isothermal crystallization kinetics of chalcogenide Se79Te20Pb1 glass using differential scanning calorimetry technique

In the present paper, the overall amorphous-crystallization transformation kinetics of chalcogenide Se79Te20Pb1 alloy has been reported using differential scanning calorimetry technique under non-isothermal conditions at three different heating rates (5, 10 and 15 °C/min). Amorphous nature of the investigated alloy is verified using X-ray diffraction. The glass transition region has been investigated using three empirical approaches and consonance of these methods has been discussed. The apparent activation energy for glass transition and crystallization region has been deduced using different methods. The Avrami exponent of the investigated alloy indicates one dimension growth of the investigated glass. The deduced values of Hruby’s parameter and fragility index indicate that amorphous alloy has been formed from good glass forming liquids

Kinetics of Amorphous-Crystalline Transformation of Some Se-Te-In Chalcogenide Glasses Using Gao and Wang Model

The present study reports the assessment of activation energy for crystallization and crystallization reaction order (Avrami exponent n) for the amorphous-crystallization transformation process of Se85 − xTe15Inx (x 2, 6 and 10) amorphous alloys using differential scanning calorimetry (DSC) technique under non-isothermal conditions at four different heating rates (5, 10, 15 and 20 °C/min) through Gao and Wang model. The introduction of In to the Se-Te system is found to bring a change in crystallization mechanisms and dimensions of growth. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3101

Iso-conversional study of crystallization activation energy of amorphous-crystallization transformation for Se79Te20Pb1 glass using non-isothermal differential scanning calorimetry technique

135-140The ternary Se79Te20Pb1 chalcogenide glass is prepared using melt quenching technique. Differential scanning calorimetry technique (DSC) is used to investigate the kinetics of crystallization of amorphous-crystallization (a-c) phase transformation under non-isothermal conditions at three different heating rates; 5, 10 and 15° C min-1. The variation of crystallized activation energy (Ec) with crystallized fraction (ϰ) and hence, with temperature (T) is investigated using five iso-conversional methods namely KAS, OFW, Friedman, Tang and Chen and Starink. It is found that Ec is not constant but vary with ϰ as well as T. Thus, the iso-conversional analysis of investigated glass indicates that the assumption of constant Ec is not appropriate

Dielectric Properties and AC Conductivity Measurements of Amorphous Ge15Se85 Glass

In the present study, investigations of dielectric parameters viz dielectric constant (), dielectric loss () and AC conductivity measurements have been made for bulk chalcogenide Ge15Se85 glass in the frequency range 10 to 500 kHz within the temperature range from 300 to 390 K. The variation of dielectric constant and dielectric loss with frequency at room temperature is reported and discussed in the investigated glassy binary alloy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3101

Iso-conversional study of crystallization activation energy of amorphous-crystallization transformation for Se79Te20Pb1 glass using non-isothermal differential scanning calorimetry technique

The ternary Se79Te20Pb1 chalcogenide glass is prepared using melt quenching technique. Differential scanning calorimetry technique (DSC) is used to investigate the kinetics of crystallization of amorphous-crystallization (a-c) phase transformation under non-isothermal conditions at three different heating rates; 5, 10 and 15° C min-1. The variation of crystallized activation energy (Ec) with crystallized fraction (ϰ) and hence, with temperature (T) is investigated using five iso-conversional methods namely KAS, OFW, Friedman, Tang and Chen and Starink. It is found that Ec is not constant but vary with ϰ as well as T. Thus, the iso-conversional analysis of investigated glass indicates that the assumption of constant Ec is not appropriat

Dielectric Relaxation of Benzonitrile in Benzene

The dielectric constant, ε , and dielectric loss, ε , of dilute solutions of benzonitrile (C 6 H 5 CN) in benzene have been measured at 9.885 GHz at 25, 30, 35, and 40 • C using standard standing microwave techniques. Following the single frequency concentration variational method of Gopala Krishna, the dielectric relaxation time, τ, and the dipole moment, µ, at various temperatures have been calculated. It was concluded that dielectric relaxation processes can be treated as rate processes just like the viscous flow process. Based on the above studies, the monomer structure of benzonitrile in benzene has been inferred. The solute-solvent molecular association of benzonitrile in benzene has been found. The energy parameters ∆H ε , ∆F ε , ∆S ε for the dielectric relaxation process of benzonitrile in benzene at different temperatures have been calculated and compared with the corresponding energy parameters ∆H η , ∆F η , ∆S η for the viscous flow process

Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Understanding the health consequences associated with exposure to risk factors is necessary to inform public health policy and practice. To systematically quantify the contributions of risk factor exposures to specific health outcomes, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 aims to provide comprehensive estimates of exposure levels, relative health risks, and attributable burden of disease for 88 risk factors in 204 countries and territories and 811 subnational locations, from 1990 to 2021. Methods: The GBD 2021 risk factor analysis used data from 54 561 total distinct sources to produce epidemiological estimates for 88 risk factors and their associated health outcomes for a total of 631 risk–outcome pairs. Pairs were included on the basis of data-driven determination of a risk–outcome association. Age-sex-location-year-specific estimates were generated at global, regional, and national levels. Our approach followed the comparative risk assessment framework predicated on a causal web of hierarchically organised, potentially combinative, modifiable risks. Relative risks (RRs) of a given outcome occurring as a function of risk factor exposure were estimated separately for each risk–outcome pair, and summary exposure values (SEVs), representing risk-weighted exposure prevalence, and theoretical minimum risk exposure levels (TMRELs) were estimated for each risk factor. These estimates were used to calculate the population attributable fraction (PAF; ie, the proportional change in health risk that would occur if exposure to a risk factor were reduced to the TMREL). The product of PAFs and disease burden associated with a given outcome, measured in disability-adjusted life-years (DALYs), yielded measures of attributable burden (ie, the proportion of total disease burden attributable to a particular risk factor or combination of risk factors). Adjustments for mediation were applied to account for relationships involving risk factors that act indirectly on outcomes via intermediate risks. Attributable burden estimates were stratified by Socio-demographic Index (SDI) quintile and presented as counts, age-standardised rates, and rankings. To complement estimates of RR and attributable burden, newly developed burden of proof risk function (BPRF) methods were applied to yield supplementary, conservative interpretations of risk–outcome associations based on the consistency of underlying evidence, accounting for unexplained heterogeneity between input data from different studies. Estimates reported represent the mean value across 500 draws from the estimate's distribution, with 95% uncertainty intervals (UIs) calculated as the 2·5th and 97·5th percentile values across the draws. Findings: Among the specific risk factors analysed for this study, particulate matter air pollution was the leading contributor to the global disease burden in 2021, contributing 8·0% (95% UI 6·7–9·4) of total DALYs, followed by high systolic blood pressure (SBP; 7·8% [6·4–9·2]), smoking (5·7% [4·7–6·8]), low birthweight and short gestation (5·6% [4·8–6·3]), and high fasting plasma glucose (FPG; 5·4% [4·8–6·0]). For younger demographics (ie, those aged 0–4 years and 5–14 years), risks such as low birthweight and short gestation and unsafe water, sanitation, and handwashing (WaSH) were among the leading risk factors, while for older age groups, metabolic risks such as high SBP, high body-mass index (BMI), high FPG, and high LDL cholesterol had a greater impact. From 2000 to 2021, there was an observable shift in global health challenges, marked by a decline in the number of all-age DALYs broadly attributable to behavioural risks (decrease of 20·7% [13·9–27·7]) and environmental and occupational risks (decrease of 22·0% [15·5–28·8]), coupled with a 49·4% (42·3–56·9) increase in DALYs attributable to metabolic risks, all reflecting ageing populations and changing lifestyles on a global scale. Age-standardised global DALY rates attributable to high BMI and high FPG rose considerably (15·7% [9·9–21·7] for high BMI and 7·9% [3·3–12·9] for high FPG) over this period, with exposure to these risks increasing annually at rates of 1·8% (1·6–1·9) for high BMI and 1·3% (1·1–1·5) for high FPG. By contrast, the global risk-attributable burden and exposure to many other risk factors declined, notably for risks such as child growth failure and unsafe water source, with age-standardised attributable DALYs decreasing by 71·5% (64·4–78·8) for child growth failure and 66·3% (60·2–72·0) for unsafe water source. We separated risk factors into three groups according to trajectory over time: those with a decreasing attributable burden, due largely to declining risk exposure (eg, diet high in trans-fat and household air pollution) but also to proportionally smaller child and youth populations (eg, child and maternal malnutrition); those for which the burden increased moderately in spite of declining risk exposure, due largely to population ageing (eg, smoking); and those for which the burden increased considerably due to both increasing risk exposure and population ageing (eg, ambient particulate matter air pollution, high BMI, high FPG, and high SBP). Interpretation: Substantial progress has been made in reducing the global disease burden attributable to a range of risk factors, particularly those related to maternal and child health, WaSH, and household air pollution. Maintaining efforts to minimise the impact of these risk factors, especially in low SDI locations, is necessary to sustain progress. Successes in moderating the smoking-related burden by reducing risk exposure highlight the need to advance policies that reduce exposure to other leading risk factors such as ambient particulate matter air pollution and high SBP. Troubling increases in high FPG, high BMI, and other risk factors related to obesity and metabolic syndrome indicate an urgent need to identify and implement interventions