Bulk chemical composition of samples recovered from asteroid Ryugu
— Analysis of extraterrestrial material by WDXRF and TG-MS —
Hisashi Homma and Kazuko Motomura
Spacecraft HAYABUSA2 successfully collected a 5.4 g sample from the surface of asteroid Ryugu that was returned to Earth on Dec. 6, 2020. Analysis of the asteroid Ryugu sample was performed using a ZSX Primus IV wavelength dispersive X-ray spectrometer and a Thermo plus EVO2 TG-DTA8122 thermogravimetric differential thermal analyzer coupled with GC-MS (TG-MS).
A very small (24 mg) Ryugu sample (C0108) was analyzed by XRF in powder form without any pelletization or thin film covering. Analytical results by the fundamental parameter (FP) method for 23 elements including carbon and oxygen were consistent with the values from other analytical methods. Elemental abundance in Ryugu shows close similarity with the abundance determined for the CI chondrite meteorite, whose composition is the most primitive and similar to solar system elemental abundance.
About 1 mg of Ryugu sample grain A0040 was used for the TG-MS measurement. Total H₂O and CO₂ content of the Ryugu sample were 6.8 and 5.5 mass%, respectively. The Ryugu sample contains less H₂O than CI chondrite does. The TG-MS measurement reveals differences in H₂O release behavior at low temperature (< 300°C) between Ryugu and CI chondrite.
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Dramatic Improvement in The Throughput of X-Ray Topography
Kenta Shimamoto
Rigaku launched a high-speed X-ray topography system with the improved throughput of 10–20 wafers/hour (3–6 min/wafer). High-speed image acquisition is achieved using an uncollimated divergent beam and the HyPix-3000HE hybrid pixel detector. This technical note explains two major features that contribute to this improvement by dramatically reducing the time for alignment and the travel distance of the specimen to obtain topographic images of the whole area. This high-speed X-ray topography system is poised to play a key role in the quality control of wafers.
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Powder X-Ray Diffraction Basic Course Fifth Installment: Quantitative Analysis
Takahiro Kuzumaki
Powder X-ray diffraction is widely used as an analytical method to evaluate various crystalline materials. This paper describes the basics and evaluation examples of the RIR (Reference Intensity Ratio) method and the Rietveld method.
In the RIR method, quantitative analysis is performed based on the integrated intensity of diffraction peaks and the RIR values registered in databases. In this method, rapid quantitative analysis is performed once qualitative analysis has been completed. However, if the peak intensity ratio differs from that in the database due to preferred orientation or other reasons, the obtained quantitative values will be inaccurate.
The Rietveld method is a method for refining crystal structure parameters by fitting a calculated pattern obtained from lattice parameters, crystal system, atomic coordinates, etc., to a measured diffraction pattern using the least-squares method. The obtained scale factor and information about the crystal structure can be used for quantitative analysis. The Rietveld method enables accurate quantitative analysis even if samples have preferred orientation and/or complex diffraction patterns.
The combination of the Rietveld method with the internal standard method, known as the PONKCS (partial or no known crystal structure) method, and the RIR method also enable quantitative analysis of amorphous phases.
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Powder X-Ray Diffraction Basic Course Sixth Installment: Evaluation of Crystallite Size
Masaaki Konishi
Powder X-ray diffraction (PXRD) can obtain a variety of information, not just a single piece of information. In the fifth installment of the powder X-ray diffraction basic course, quantitative analysis was described. This sixth installment describes the evaluation of crystallite sizes.
The Scherrer method is one analysis technique commonly used to evaluate crystallite sizes. This method assumes there is no crystallite size distribution or lattice strain, and simply calculates the crystallite size from the width of a single diffraction peak using the Scherrer equation. This method requires the measurement of a width standard material to correct the width to obtain an accurate crystallite size.
On the other hand, evaluation of crystallite sizes using a FP (Fundamental Parameter) method can be corrected by calculating the width attributed to the equipment. This method can analyze crystallite sizes less than 300 nm with an accuracy of a few nm regardless of the optical system conditions and measurement instruments. Even for large crystallite sizes of 100–300 nm, it is possible to calculate highly accurate crystallite sizes and their distributions and, furthermore, to evaluate them accounting for crystallite anisotropy.
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XSPA-400 ER - X-Ray Seamless Pixel Array Detector
The XSPA-400 ER (XSPA: X-ray Seamless* Pixel Array, ER: Energy Resolution) is a next-generation 2D semiconductor detector with a higher energy resolution than conventional models. With this higher energy resolution, the XSPA-400 ER reduces X-ray fluorescence, which can be a significant source of background intensity for powder diffraction patterns on samples containing transition metal elements. In addition to 0D and 1D measurements, 2D measurements are also available. The 2D mode allows the user to observe Debye-Scherrer rings, which provide information about sample orientation and the existence of coarse particles. Furthermore, the 75 μm× 75 μm pixel size provides high spatial resolution. These features contribute to improved accuracy in quantitative analysis of trace crystalline phases, precise analysis of lattice constants, and 2D stress analysis of samples such as steel and battery materials that contain transition metal elements.
*Seamless Pixel Detectors: Typical hybrid pixel detectors use a tiled array of readout ASICs (Application Specific Integrated Circuits). With these tiled array detectors the pixel shapes at the IC boundary differ from those in other areas on the IC, requiring correction of the IC boundary. In addition, the correction sometimes remains incomplete depending on the measurement conditions, leaving an intensity difference between the boundary and other non-boundary areas on the IC. As a better solution, the seamless pixel detector has the same pixel shape over the whole IC, eliminating the need for IC boundary correction and thus producing a uniform image.
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