Application of x-ray absorption fine structure (XAFS) to local-order analysis in Fe-Cr maghemite-like materials AIP Conference Proceedings 1671, 020008 (2015) Abstract.In Chihuahua State, a little town called Naica has the largest gypsum single crystals in the world. The growth of these structures has been described as a long and stable process developed over thousands of years. Due to the change in the environmental conditions, these crystals could suffer alterations on their surface. In this project we study the cause of possible deterioration of the giant crystals and intend to suggest measures for their preservation. For this sake, our first experiment consists on several gypsum crystals that have been subjected in a climate chamber to a fog at high CO 2 concentration and 51 °C for a period of time of six months, extracting two crystals every 15 days. Then the crystals have been characterized through Grazing Incidence X-Ray Diffraction using a diffractometer PanAlytical X'PertPro with two different detectors; Xe-filled proportional detector and a Pixel 3D detector. The results were compared to determine which technique is the most suitable to study the degradation of gypsum single crystals. In the two cases, we have identified only the gypsum phase, but with different crystal plane orientations.
The purpose of this work is to determine the effective piezoelectric coefficient (d 33 ) and the macro ferroelectric hysteresis behavior for the Ba 0.9 Ca 0.1 Ti 0.9 Zr 0.1 O 3 (BCZT). The sample was prepared by the modified Pechini method and it was sintered at 1250 ºC for 5 h. The refinements of X-ray diffraction (XRD) patterns obtained by the Rietveld method suggest a slight degree of tetragonality (c/a = 1.0025) in the perovskite structure. High counting statistics was performed in the two-dimensional grazing incidence 2D-GIXRD characterization by using synchrotron radiation. These results and the Raman spectrum analysis support the XRD interpretation. The morphology reveals a non-homogeneous terrace-type shape with a grain size distribution centered at 13 microns. The switching spectroscopy piezo-response force microscopy was used to obtained the effective d 33 = 142 pm/V. The soft ferroelectric hysteresis shows a coercive field H c = 1.3 kV/cm with a saturation polarization P s = 15.7 µC/cm 2 .
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