Abstract
A compact laboratory X-ray scattering platform that uniquely enables for high-performance ultra-small-angle X-ray scattering (USAXS), small- and wide-angle X-ray scattering (SAXS/WAXS), and total scattering (atomic pair distribution function analysis; PDF) experiments was developed. It covers Bragg spacings from sub-Angstroms to 1.7 μm, thus allowing the analysis of dimensions and complex structures in (nano-)materials on multiple length scales. The accessible scattering vector q-range spans over almost five decades (qmin = 0.0036 nm-1, qmax = 215 nm-1), without any gaps. Whereas SAXS is suitable to characterize materials on a length scale of 1-100 nm, with USAXS, this range can be significantly extended to the micrometer range. On the other end, from WAXS and particularly from PDF measurements, information about the local atomic order and disorder can be obtained. The high performance, exceptional versatility, and ease-of-use of the instrument are enabled by a high-resolution 2-circle goniometer with kinematic mounts, a modular concept based on prealigned, quickly interchangeable X-ray components, and advanced detector technology. For USAXS measurements, a modified Bonse-Hart experimental setup with single crystal collimator and analyzer optics is used. SAXS/WAXS measurements are enabled by focusing optics, an evacuated beam path, and a 2D detector. For total scattering experiments, a high-energy X-ray source is used in combination with a hybrid pixel array detector that is based on a CdTe sensor for the highest counting efficiency. To ensure high resolution and sensitivity in these various applications, special care is taken to suppress any type of background scattering signal. The high resolution that can be achieved with the USAXS collimation system is demonstrated on a set of monodisperse, colloidal silica dispersions and derived colloidal crystals, with particle diameters in the range of hundreds of nanometers up to 1.6 µm. USAXS and SAXS results are shown to be consistent with those obtained by static light scattering (SLS) and dynamic light scattering. It is demonstrated that the obtainable USAXS data bridge the gap in q between SAXS and SLS. The capabilities of the instrument to acquire high-quality total scattering data for PDF analysis are demonstrated on amorphous SiO2 nanoparticles as well as on NaYF4 upconversion nanocrystals. To the best of our knowledge, it is for the first time that we present a single laboratory instrument that enables measurements of high-quality X-ray scattering data within such a wide q-range, by combining four complementary elastic X-ray scattering techniques. The modular design concept of the instrument allows for incremental improvements as well as to add more applications in the future.
Highlights
X-ray scattering and diffraction techniques[1,2,3,4,5,6] are widely used for the nondestructive analysis of micro- and nanostructures in matter, and for investigations on the arrangement of atoms in crystal structures
As we have shown previously, good quality total scattering data can be measured on an optimized lab instrument,[48,63] and the deduced pair distribution function (PDF) compare well with those obtained from synchrotron radiation data.[54]
A highly versatile, compact laboratory instrument that enables a variety of X-ray scattering techniques for the structural and dimensional characterization of matter on multiple length scales has been presented
Summary
X-ray scattering and diffraction techniques[1,2,3,4,5,6] are widely used for the nondestructive analysis of micro- and nanostructures in matter, and for investigations on the arrangement of atoms in crystal structures. Large distances (several meters) between the X-ray source and the sample, as well as between the sample and detector, are often necessary to achieve a good small-angle and point-to-point resolution Due to these demanding requirements for the experimental setup, SAXS measurements are traditionally performed on single-purpose lab instruments or on dedicated beamlines at synchrotron radiation facilities.[6] Modern SAXS instruments enable extension of the measurement range toward higher scattering angles, for the acquisition of complementary WAXS data. We have recently presented a new concept of instrumentation for high-performance SAXS/WAXS measurements,[33] which makes use of a goniometer-based XRD system, as widely used for powder X-ray diffraction and related techniques. The USAXS and total scattering techniques are closely related and complementary to SAXS and WAXS When combined, these techniques enable the analysis of complex structures in hard and soft matter, covering multiple length scales. All information about the instrument configuration and the scan parameters are stored in an open, XML-based file format.[33]
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