Review of Research on the Thermoelectric Material ZnSb

The thermoelectric material ZnSb has been studied intensively in recent years and has shown promising features. The other zinc‐antimonide compound, Zn4Sb3 has remarkable low thermal conductivity, but it is accompanied with phase transitions at moderate temperature and has inherent stability problems. Compared to that, ZnSb is relatively phase stable and has a relative high charge carrier mobility and Seebeck coefficient, thus yielding a decent power factor. Meanwhile, its thermal conductivity can be reduced by means of nanostructuring, thus giving a good figure of merit at moderate temperatures, 400–600 K. Many researchers have dedicated their efforts to study and improve ZnSb properties, and the figure of merit has been reported to be above one. Still, ZnSb as a thermoelectric material has features and behaviours that are not well‐understood. The behaviour and properties of its intrinsic defects are not understood, but have interested researchers in recent years. This chapter intends to offer a comprehensive review on ZnSb to the readers. By combining own experiences from research on thermoelectric materials, the authors address the prospect for improving the thermoelectric properties of ZnSb and the concerns of transferring lab results to manufacturing

Silicide formation with bilayers of Pd-Pt, Pd-Ni, and Pt-Ni

Evaporated two-layered thin films of Pd-Ni, Pt-Ni, and Pt-Pd on single-crystal Si have been vacuum annealed in the temperature range 200–900°C. The sequence of films as well as substrate orientation have been varied. The silicide formation has been studied by MeV He + backscattering spectrometry and glancing angle x-ray diffraction. The silicide layers are highly inhomogeneous in the elemental depth distribution for annealing below 600°C. Above 700°C, the distributions become homogeneous. The silicide-substrate interface shows varying sharpness depending upon substrate orientation and evaporation sequence. We suggest the existence of ternary monosilicides of the type Pt1–xPdxSi, Pt1–xNixSi, and Pd1–xNixSi. The Pt1–xPdxSi ternary silicide is stable up to 900°C; the others are not

Growth of Ge Nanoparticles on SiO2/Si interfaces during Annealing of Plasma Enhanced Chemical Vapor Deposited Thin Films

Cataloged from PDF version of article.Multilayer germanosilicate (Ge:SiO2) films have been grown by plasma enhanced chemical vapor deposition. Each Ge:SiO2 layer is separated by a pure SiO2 layer. The samples were heat treated at 900 degrees C for 15 and 45 min. Transmission electron microscopy investigations show precipitation of particles in the layers of highest Ge concentration. Furthermore there is evidence of diffusion between the layers. This paper focuses mainly on observed growth of Ge particles close to the interface, caused by Ge diffusion from the Ge:SiO2 layer closest to the interface through a pure SiO2 layer and to the interface. The particles grow as spheres in a direction away from the interface. Particles observed after 15 min anneal time are 4 nm in size and are amorphous, while after 45 min anneal time they are 7 nm in size and have a crystalline diamond type Ge structure. (C) 2006 Elsevier B.V. All rights reserved

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5~eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70~nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25~eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper

The JDCS model and blue-collar bullying: Decent working conditions for a healthy environment

Violence in the workplace and its health consequences still represent one of the main obstacles to obtaining decent working conditions. In particular, blue-collar workers run a greater risk of experiencing episodes of violence, also because of a lack of autonomy and fewer social interactions. According to the work environment hypothesis, factors such as high workload, lack of social support and lack of job control represent the antecedents of workplace bullying. Following the job demand-control-support model (JDCS), violence can be the symptom of a high-strain environment. Moreover, it is still unclear if workplace bullying can mediate the effects of work-related stress on workers’ health outcomes. The aim of the present study is to analyse the relationship between the components of the JDCS and the health of the workers considering workplace bullying as a mediating variable. By a cross sectional study design, we tested the following theoretical hypotheses: first, JDCS components (conceptualized as stress) are supposed to significantly predict the level of workers’ health. Second, workplace bullying is supposed to mediate the relationship between the JDCS components and the level of health. The sample consists of 400 blue-collars from three different Italian companies. Work-related stress, health outcomes and workplace bullying were measured by specific self-administered questionnaires and the relationships between the variables of interest were tested through a structural equation model (SEM) analysis. The results showed that while the direct relationship between the components of the JDCS and the level of psychological health is weaker (standardized path coefficients SPC = 0.21), the partial mediation hypothesis shows that workplace bullying mediate the relationship between JDCS components and health outcomes (χ2/df ratio = 2.70; path from stress to workplace bullying SPC = 0.78; path from workplace bullying to general health SPC = 0.51; p = 0.01). The JDCS components (workload, lack of control, lack of support) are useful predictors for workplace bullying. On the other hand, bullying plays a mediating role between the stress experienced and the health consequences. The present study adds new insights into the relationship between violence seen as a form of social behavioural strain and the psychological health of workers. The theoretical and practical implications are discussed. Future research on blue-collars could use longitudinal designs in order to analyse the relationship between social environment, job design and strain reactions