A Beryllium Dome Specimen Holder for Xrd Analysis of Air Sensitive Materials

A specially designed specimen holder employing a beryllium dome has been fabricated for collection of XRD data from highly reactive materials. The specimen holder has a robust o-ring type seal (>10 torr) and no observed intensity artifacts in the 1° to 150° 2θ range. The design also minimizes specimen displacement errors and allows for analysis of both powders and bulk specimens (i.e., pellets). The simple design makes for straightforward assembly of the holder within the confines of a glove box. XRD analysis of hygroscopic LaBr3 powders collected with this holder are suitable for Rietveld structure refinement, yielding unit cell lattice parameters of a = 7.9703(6) Å and c = 4.5122(6) Å; cell volume = 248.44(6) Å; Rp = 7.70%. INTRODUCTION Analysis of highly air-sensitive materials by X-ray diffraction has always been challenging. Many methods that circumvent this issue have been implemented in the past such as mixing the specimen with an inert compound, sealing the material between two pieces of thin mylar doublestick tape, or placing powder materials in a capillary tube [1]. However, these preparations may not be well suited for quantitative analysis as they often suffer from eventual reaction because of leakage of the medium material. Furthermore, the holder material will likely contribute significant artifact in the diffraction pattern. For more quantitative XRD analysis, a variety of holders have been prepared using various window materials [2–6]. Our review of these holders yielded insight into the important aspects of a functional holder for XRD analysis, as well as potential pitfalls. Issues such as clearance height and width within an instrument, access to lowangle data, susceptibility to specimen displacement errors, quality of seal for inert atmosphere, and presence of artifact were some of the relevant issues regarding fabrication of a functional holder. Our recent investigation of rare-earth halide materials demonstrated a need for a more robust method of XRD analysis on highly hygroscopic materials. It was our desire to obtain high-quality XRD data from lanthanum bromide (LaBr3) and other rare-earth halides. This analysis proved difficult or impossible with some of the methods discussed earlier. We desired to have a sample holder that would maintain an excellent seal (leak rate <1×10 torr) for sufficient time to obtain a Rietveld quality diffraction pattern (i.e., ~12 to 18 h). Additional criteria regarding the holder included that it be easily assembled within an inert atmosphere glove box, minimize sample displacement errors, and be free of intensity artifacts associated with the holder. We also desired to configure the holder so that it could be easily modified for various XRD systems and configurations. We present the results of our study. 55 Copyright ©JCPDS-International Centre for Diffraction Data 2008 ISSN 1097-0002