Properties of spark plasma sintered nanostructured Zn_1+xSb

Abstract

Engineering materials with specific physical properties has recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium and long-wavelength phonons lowering thereby the thermal conductivity of the system without simultaneously decreasing the charge transport (phonon-glass electron-crystal concept). A new Zn1+xSb nanophase obtained by a wet chemical approach was densified by spark plasma sintering (SPS). Investigations on compounds subsumed as "Zn4Sb3" always suffer from its low thermal stability and the contamination of the nanoparticles with solvents and additives used in the synthesis. In order to gain insight into this compound's electronic properties we investigated a material free from remnants of the synthesis but contaminated with a small amount of well-characterized decomposition product, i.e., ZnSb. To investigate the influence of the sintering process on the densified samples, different SPS conditions were applied. Four different conditions were used with heating rates between 160° and 230 °C/min, sintering temperatures between 130 and 190 °C and sintering times between 3 and 6 min. Powders from the surface of the pellets were subject to powder X-ray diffraction (XRD) yielding information about the surface composition. Small pieces of the pellets were also characterized using high-energy synchrotron radiation scattering in order to reveal the phase compositions inside the pellets. Small changes in the sintering conditions of the samples were found to have a large influence on the resulting sample compositions. In addition, the phase compositions on the surface differ significantly from the ones inside the pellets which show a much higher grade of decomposition. The density and morphology of the obtained pellets have been investigated by means of laser microscopy and scanning electron microscopy (SEM). The low density and porosity of the different pellets is a result of the graphite pressing tool which has to be used to ensure the temperature control during the SPS process

Fast Direct Synthesis and Compaction of Homogenous Phase-Pure Thermoelectric Zn4Sb3

“…β-Zn 4 Sb 3 is also of interest, because it is among the cheapest thermoelectric materials known, and it is made of relatively nontoxic elements. , However, the instability of Zn 4 Sb 3 in the working temperature range may limit its practical use in thermoelectric applications. β-Zn 4 Sb 3 is known to degrade even below 500 K in air by the loss of Zn and growth of ZnSb, Sb and Zn (or its oxidation compound ZnO) as degradation products. ,− Recently a new window of stability for the β-Zn 4 Sb 3 was discovered from 565 to 767 K, which might open up for further utilization of β-Zn 4 Sb 3 at higher temperatures …”

Geometry-induced electron doping in periodic semiconductor nanostructures

“…Both are 2D in nature. However, a 3D approach to modulation doping was introduced in [8] to improve the thermoelelectric characteristics of nanocomposites [9,10]. The influence of periodic structures on electronic properties has been studied in related geometries, such as periodic curved surfaces [11,12], nanotubes [13], cylindrical surfaces with nonconstant diameter [14], and strain-driven nanostructures [15].…”

Thermoelectric properties of spark-plasma sintered nanoparticular FeSb2prepared via a solution chemistry approach

“…As a consolidation method spark plasma sintering (SPS) was shown to be a suitable tool for the densification of FeSb 2 in particular and intermetallic nanoparticles in general. [25][26][27][28][29] With exceptional heating and cooling rates (>100 K min −1 ), particle growth is suppressed and densification mechanisms such as grain boundary diffusion, volume diffusion and particle rearrangement are promoted.…”