Microstructural evolution and thermal stability of AlCr(Si)N hard coatings revealed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction
The beta-phase of Zn4Sb3 has been regarded as a very promising thermoelectric material since middle nineties, owing to its unique merit: intermediate temperature region (200-400 °C), made of cheap, non-toxic and abundant elements and high thermoelectric property. However, the thermal stability of Zn4Sb3 seems to be an inherent obstacle for the practical application during the working temperatures. Herein, magnesium doped Zn-Sb semiconductor (Mg0.04Zn3.96Sb3) was investigated thoroughly in-situ during thermal annealing up to 600 K, whilst both microstructure and electronic structures were recorded via the combination of synchrotron-based two dimensional X-ray diffraction techniques and the X-ray photoemission spectroscopy. While the time-resolved grazing incidence XRD reveals the preserved crystal structures during thermal annealing to 600 K, XPS measurement demonstrate the robustness of electronic structures. On basis of these findings, it was concluded in the end that the doping of magnesium significantly improves the thermal stability of zinc-antimonite compounds and introduces minor influence on the electronic structure of Zn-Sb alloy. Our study may propose an effective approach towards the wild application of Zn4Sb3 related thermoelectric materials.
AbstractThe dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides is not yet fully understood. In this contribution, three Al0.7Cr0.3N thin films with residual stress magnitudes of −3510, −4660 and −5930 MPa in the as-deposited state were in-situ characterized in the range of 25–1100 °C using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction and temperature evolutions of phases, coefficients of thermal expansion, structural defects, texture as well as residual, thermal and intrinsic stresses were evaluated. The multi-parameter experimental data indicate a complex intrinsic stress and phase changes governed by a microstructure recovery and phase transformations taking place above the deposition temperature. Though the decomposition temperatures of metastable cubic Al0.7Cr0.3N phase in the range of 698–914 °C are inversely proportional to the magnitudes of deposition temperatures, the decomposition process itself starts at the same stress level of ~−4300 MPa in all three films. This phenomenon indicates that the particular compressive stress level functions as an energy threshold at which the diffusion driven formation of hexagonal Al(Cr)N phase is initiated, provided sufficient temperature is applied. In summary, the unique synchrotron experimental setup indicated that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides.
Binary compound Y3Fe29cannot be directly formed by rare earth Y and Fe and the third element M (non-iron transition elements) must be introduced to form ternary compound Y3(Fe,M)29. In this work, six alloys with compositions of the Y3Fe29-xCrx(x=1,2,3,4,5,6) were prepared and investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and differential thermal analysis (DTA). The study on the thermal stability of these compounds points to that the compoundY3(Fe,Cr)29is a high temperature phase and exists above 1100K. The alloys with single-phase of Y3(Fe,Cr)29was decomposed into Y2(Fe,Cr)17and Y(Fe,Cr)12annealed at high temperature 1100K.
Thermal stability of wurtzite Zr1−xAlxN coatings studied by in situ high-energy x-ray diffraction during annealing