Automated and Evacuated X-ray Optics for Improved Qualitative and Quantitative Phase Analysis

1 Introduction

X-ray diffraction (XRD) is a standard method for the quantitative and qualitative analysis of polycrystalline samples, such as powders or bulk materials. Identifying all phases contained in a material and quantifying the correct relative amount of each phase can be difficult. This is especially true in multiphase systems where certain phases only make up a few percent of the whole. High data quality, with good resolution and low background noise, helps immensely in this regard. While the quality of an XRD measurement is in part determined by sample properties, it can be significantly improved by using the best possible hardware setup that is optimized for the highest data quality. Anton Paar’s automated multipurpose powder X-ray diffractometer XRDynamic 500 is the perfect choice for such measurements, as its patented TruBeam^TM concept combines unparalleled data quality with high versatility and measurement efficiency.

1.1 TruBeam^TM

The TruBeam™ concept comprises several hardware and technical features that deliver these benefits in data quality and measurement efficiency. The goniometer radius of 360 or 400 mm is larger than what is typically found in powder XRD instruments, leading to extremely high measurement resolution. One possible drawback of a large radius is that the beam has to pass through a lot of air resulting in higher background and reduced intensity due to air scattering and absorption of the beam in air. This problem is overcome by the unique, fully evacuated optics units of XRDynamic 500. The decreased air scattering due to the evacuated beam path leads to a lower measurement background, higher signal-to-noise ratio, and better overall data quality. TruBeam^TM also uniquely features full automation of all beam optics, allowing complex measurements with different divergence slit sizes, beam masks and Soller slits to be programmed in the same experiment. The beam geometry can also be automatically switched during experiments, making it possible to first measure a sample in Bragg-Brentano geometry with a Kβ filter and then with a monochromator without any manual interaction with the instrument in between. Together with the large variety of sample stages available for XRDynamic 500, this enables an incredible variety of complex experiments with unparalleled efficiency. Six of the seven measurements presented in this application report were obtained without any manual interaction with the instrument.

1.1 Motivation

The goal of the measurements presented in this application report was to investigate and visualize how large the impact of different optical components is on the data quality of XRD measurements, and how this can influence the possibility to detect phases present in very low concentrations. Two samples, calcium carbonate (CaCO₃) mixed with rutile (TiO₂), and calcium carbonate mixed with glucose (C₆H₁₂O₆), were prepared in different relative amounts. CaCO₃ is a versatile material that is found both in food science, where it can occur as a mixture with glucose, and in building materials or paints, where it can occur together with TiO₂. The samples investigated represent the types of materials that scientists may encounter in their everyday routine measurements.