The thermal stability of the high performance n-type Te-doped Mg3Sb1.5Bi0.5 system is investigated.

The structure and thermal stability of thermoelectric (TE) SrZn2Sb2 have been probed by means of both in situ and ex situ powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry, and inductively coupled plasma optical emission spectrometry. Densification of the sample during synthesis induced evolution of an increasing degree of impurity phases coming from the decomposition of SrZn2Sb2. Variable-temperature synchrotron powder X-ray diffraction experiments performed on an air-packed sample revealed a structural breakdown occurring between 500 and 600 K. DSC performed in an argon flow revealed the decomposition to be an exothermic and kinetically slow transition accompanied by a weight loss of zinc, showing the extent of decomposition to increase as a function of decreasing heating rate applied in the DSC experiments. Using the Kissinger and Ozawa analysis methods, activation energies of ≈1.9 eV were obtained. After five days at 850 K in vacuum, argon, and air atmospheres, cold-pressed samples showed a complete depletion of SrZn2Sb2, however, the zinc evaporation was strongly inhibited compared to the DSC experiments, which is likely to be because of the reduced surface area. These observations indicate that the structural decomposition is independent of both operating atmosphere and surface-to-volume ratio, making SrZn2Sb2 unsuitable for practical TE applications in intermediate- and high-temperature environments in spite of the promising TE properties reported previously.

In recent years hierarchical thermoelectric materials have been engineered to reach record breaking thermoelectric figures-of-merit (zT) making them attractive in green transition energy conversion applications. PbTe constitutes an archetypical example,...

Here, we report on adding an important dimension to the fundamental understanding of the evolution of the thin film micro structure evolution. Thin films have gained broad attention in their applications for electro-optical devices, solar-cell technology, as well storage devices. Deep insights into fundamental functionalities can be realized via studying crystallization microstructure and formation processes of polycrystalline or epitaxial thin films. Besides the fundamental aspects, it is industrially important to minimize cost which intrinsically requires lower energy consumption at increasing performance which requires new approaches to thin film growth in general. Here, we present a state of the art sputtering technique that allows for time-resolved in situ studies of such thin film growth with a special focus on the crystallization via small angle scattering and X-ray diffraction. Focusing on the crystallization of the example material of BaTiO3, we demonstrate how a prototypical thin film forms and how detailed all phases of the structural evolution can be identified. The technique is shaped to enable a versatile approach for understanding and ultimately controlling a broad variety of growth processes, and more over it demonstrate how to in situ investigate the influence of single high temperature sputtering parameters on the film quality. It is shown that the whole evolution from nucleation, diffusion adsorption and grain growth to the crystallization can be observed during all stages of thin film growth as well as quantitatively as qualitatively. This can be used to optimize thin-film quality, efficiency and performance.