Diffractometer for time-resolved in-situ high temperature powder diffraction and X-ray reflectivity

亚琛大学结晶研究所(IFK)的研究课题包括温度相关的结构相变、固态反应(如脱水反应、偏析)、温度相关的氧化还原反应和(主要是陶瓷)功能材料的烧结过程。为了在原子水平上了解潜在的结构过程及其动力学，必须收集、分析和比较许多依赖温度和时间分辨的数据集。此外，我们还研究了固体与液体或气体之间的界面结构和过程。现代X射线衍射仪允许将粉末X射线衍射法(PXRD)和X射线反射率法(XRR)结合在一个设备中。使用铜辐射的检查通常由于高通量而提供高强度，因此允许在反射中对平板样品进行较短的测量时间。虽然大波长具有高的角分辨率，因此一方面具有良好的反射分辨率，但由于吸收较强，它不适合于毛细管中的透射率测量，即使对于中重元素也是如此。在这里，建议使用较短波长(因此吸收强度较小)的钼辐射。特别是，当可以使用Kα1，2波长混合物进行测量时，这种X射线源还可以提供相当大的通量，从而以合理的测量时间提供良好的强度。对于没有明确光滑表面的XRR或多晶X射线样品(例如陶瓷或金属制品和部件)，两种X射线源都需要初级Goebel反射镜。结果表明，铜的束流结构是平行的。为了用较小的样品体积获得足够高的强度，在透射式毛细测量中为钼管提供了一个聚焦Göbel镜。这也允许XRR测量和在放牧入射下的测量。在空气、真空和惰性气体中使用平板样品(反射中)和毛细管(传输中)，可在铜和钼辐射下运行的高达1200°C的高温室是IFK成功研究工作的先决条件。XRR测量需要对样品位置(x，y，z)和倾斜度进行精细的电动调整，以获得最佳的测量条件。过去，反射仪方法已经被优化，用于测量液膜，也用于同步加速器光束线，这需要振动衰减和/或样品与环境的解耦。对于快速(几分钟)的位置敏感测量，二次侧需要一个2D探测器，这适用于XRR以及铜和钼辐射的时间分辨高温衍射。

The research questions of the Institute of Crystallography (IfK) of RWTH Aachen University include temperature-dependent structural phase transformations, solid-state reactions (e.g. dewatering reactions, segregation), temperature-dependent redox reactions and sintering processes in (mostly ceramic) functional materials. To understand the underlying structural processes and their kinetics at the atomic level, many temperature-dependent and time-resolved data sets have to be collected, analyzed and compared. In addition, we study interfacial structures and processes between solids and liquids or gases. Modern X-ray diffractometers allow the methods of powder X-ray diffraction (PXRD) and X-ray reflectivity (XRR) to be combined in one device. Examinations with copper radiation usually deliver high intensities due to the high flux and therefore allow short measurement times on flat specimens in reflection. While the large wavelength enables a high angular resolution and thus a good reflection resolution on the one hand, it is not suitable for transmission measurements in capillaries even for medium-heavy elements due to the relatively strong absorption. Here, the use of shorter-wavelength (and therefore less strongly absorbed) Mo radiation is recommended. Especially, when measurements can be performed using a Kα1,2 wavelength mixture, this X-ray source also delivers considerable flux and thus good intensities with reasonable measurement times. For XRR or polycrystalline XRD samples without a defined, smooth surface (e.g. ceramic or metallic workpieces and components), primary Goebel mirrors are required for both X-ray sources. As a result, a parallel beam geometry is obtained for Cu. A focusing Göbel mirror is provided for the Mo tube for capillary measurements in transmission in order to obtain sufficiently high intensities with a small sample volume. This also allows XRR measurements and measurements under grazing incidence. A high-temperature chamber up to 1200 °C, which can be operated with both Cu and Mo radiation, under air, vacuum and inert gas with both flat samples (in reflection) and capillaries (in transmission), is a prerequisite for the successful research work of the IfK. XRR measurements require fine, motorized adjustment of the sample position (x, y, z) and tilt for optimal measurement conditions. The reflectometry method has already been optimized in the past for measuring liquid films, also on synchrotron beamlines, which requires vibration damping and/or decoupling of the sample from the environment. For fast (a few minutes), position-sensitive measurements, a 2D detector is required on the secondary side, which is suitable for XRR as well as time-resolved high-temperature diffraction with Cu and Mo radiation.