Volume 36(1) - Winter 2020

In recent years, pair distribution function (PDF) analysis has been used to characterize material structure in a wide research field. H. Kim reported the reduction mechanism in the reversible hydrogen storage capacity of V_1－xTi_x alloys. B. Li et al., reported the mechanisms of the thermoelectric effect and the phase transition to superionic conductor of AgCrSe, which is known to be a thermoelectric material at high temperature, by X-ray and neutron total scattering, and inelastic neutron scattering. K. Ohara et al. reported on the process of crystallization of Li₇P₃S₁₁, the most important material for all-solid-state Li ion batteries, carried out by a time-resolved PDF measurement at a synchrotron source. This measurement technique can be applied to investigate structural changes in real time.

In 1927, the basic theory of PDF analysis was first reported by Zernike–Prins. They reported that the structure factor observed from an X-ray scattering profile directly corresponds to the PDF. PDF analysis mainly provides local structural information, such as coordination number and average interatomic distances. PDF analysis can be applied to any sample conditions (i.e., crystalline solid, amorphous solid and fluid); however, this analysis has been mainly used for structural analysis of amorphous solids and liquid. Recently, PDF analysis has also been used to characterize the local structure of crystalline materials.

Cement is used as a raw material in the construction of buildings, tunnels, dams, and bridges. Basically, cement consists of clinker, calcium sulfate hydrate as a plaster component, aggregate, and water. The four major components of cement have different characteristics of time for hardening and strengthening of the cement; for example, alite strengthens in a short period whereas belite strengthens over a long period. Therefore, the composition of the four major components in the clinker is changed for various construction types since cement is used for a wide variety of purposes.

Ordinary Portland cement is a popular cement. The hardening speed of high early strength Portland cement with high alite concentration is much faster than for ordinary Portland cement. High early strength Portland cement is used as emergency construction concrete and winter concrete. A moderate heat Portland cement, which is used for making dams, with low heat of hydration, has a large concentration of belite. Therefore, composition analysis of clinker and cement is needed because many kinds of cements are required for various construction situations.

Composition of cement is evaluated by elemental analysis using X-ray fluorescence spectrometry (XRF) based on ASTM C114. On the other hand, X-ray diffraction (XRD), a rapid analysis method for crystalline phases, can be applied to identify components of clinker and cement in addition to quantitative analysis by Rietveld refinement because the four major components are contained in clinker as crystalline phases. In this paper, XRD was applied to cement analysis and some applications are introduced.

Because lithium-ion batteries have higher energy density than other secondary batteries, it has been possible to make them smaller and lighter. This has enabled them to spread rapidly as power sources for mobile devices such as laptop computers and cellular phones. The demand for lithium-ion batteries keeps growing relentlessly and, in recent years, the electrification of vehicles using secondary batteries has become a worldwide trend toward realizing a low-carbon society. Furthermore, because conventional liquid-state cells using an organic solvent as the electrolyte are flammable, the development of safe, all-solid-state cells using a solid electrolyte is being actively pursued in Japan and the rest of the world.

In this light, many expect the performance of lithium-ion batteries to improve further, together with longer life and better safety. X-ray diffraction (XRD) is considered one of the effective analytical techniques required to evaluate the improved performance of lithium-ion batteries.

To examine the crystallization and phase ID analysis of synthesized battery materials, lab-scale X-ray diffractometers that are readily available for research are frequently used. On the other hand, operando (or in-situ) measurement of the changes in the crystal structure of the positive and negative electrode materials during the charging and discharging processes are frequently conducted at synchrotron facilities where high-intensity X-rays are available. Recently, operando measurement has become possible even with lab-scale X-ray diffractometers due to improved performance of X-ray sources, optical elements, and detectors. This article introduces examples of characterizing lithium-ion battery materials using SmartLab.

Cement is used for concrete in construction and architectural structures. Clinker, which is an intermediate material for cement, is produced by mixing and calcinating cement raw materials such as limestone, clay and silica in a rotary kiln at a high temperature. The unreacted calcium oxide remaining after calcination of the clinker is called free lime (f.CaO).

When calcination in a rotary kiln is insufficient, limestone, the main raw material, does not react sufficiently with silicon dioxide, aluminum oxide, etc., and the amount of free lime increases, resulting in the cement not meeting the expected composition. Furthermore, free lime changes to calcium hydroxide and calcium carbonate by reacting with moisture and carbon dioxide in the air, causing volume expansion. Thus, process control of clinker is important because it directly affects the quality of the cement product.

There is no difference in the X-ray fluorescence peak profile of the Ca Kα line between free lime and other calcium compounds; therefore, the concentration of free lime cannot be determined by X-ray fluoresce (XRF) analysis. Free lime is therefore generally analyzed by wet chemical analysis like titration or by an X-ray diffractometer (XRD). This paper introduces the Rigaku simultaneous wavelength dispersive X-ray fluorescence (WDXRF) system Simultix 15 equipped with a free lime diffraction channel, enabling both XRF analysis and free lime quantification by XRD. Quantitative analysis of free lime is also described.

In the manufacturing process of semiconductor products, thin film inspection methods vary depending on the purpose. For example, optical such as ellipsometers, sheet resistance film thickness meters, step meters, and cross-sectional scanning electron microscopes (SEM) are used for film thickness management. For analysis of composition, X-ray photoelectron spectroscopy (XPS) or other techniques are used.

Among these techniques, X-ray fluorescence (XRF) spectrometers are used in many processes due to the capability to perform simultaneous film thickness/composition analysis non-destructively, with no contact and no sample preparation. The method is applicable to opaque films (metals or nitride films, etc.) and has excellent reproducibility. Special features of wavelength dispersive XRF (WDX; Wavelength Dispersive XRF) analysis are shown below;

1. Analysis of light elements such as B, N and Al
2. Sub-nm (Å) level ultra-thin film analysis
3. Analysis of layered and compound films

Due to these advantages, the use of WDXRF instruments has been increasing in recent years.

Structural biology aims to understand life from observation of relevant biological structures and then to extend that knowledge to advance medicine, pharmaceutical development and so on. Because biological systems generally have hierarchical structures, the observation of biological systems varies in size range whether one is looking at tissue level structures, cellular structures or at molecular structures. Observation of these various biological samples is currently accomplished using various methodologies, including electron microscopy and visible-light microscopy. In this report, we will discuss an X-ray imaging of structures that range in size down to sub-micrometers. The nano3DX from Rigaku is a laboratory-based high-resolution X-ray microscope that uses a high-brilliance X-ray generator, a quasi-parallel beam technology and a high-resolution X-ray camera.

A major benefit of X-ray microscopes is their ability to examine thick specimens by taking advantage of the high permeability of X-rays to observe a sample’s inner structure. X-ray microscopy bears a complementary relationship to other methodologies like electron microscopy that affords high resolution but is not suitable for thick specimens and light microscopy that allows live imaging of specimens. Further developments continue in the area X-ray microscopy, particularly for biological applications.

The modern X-ray diffractometer has drastically changed in performance compared with those from even only 10 years ago. With Hybrid Photon Counting (HPC) detector technology, brighter sources and more intelligent software, modern diffractometers enable higher quality, faster research and open new areas of study possible on smaller and more challenging samples.

The XtaLAB Synergy is a range of diffractometers from Rigaku which are designed to meet the needs of modern crystallographic researchers as multipurpose versatile diffractometers sharing a common platform. The range covers instruments from entry level microfocus systems to high performance rotating anode instruments. The instrumentation is modularised such that the core platform supports different combinations of components to make up a comprehensive range covering the needs of many different classes of user. All are powered by CrysAlis^Pro, which has an intuitive user interface which provides a consistent environment to enable users to feel at home on any instrument in the range. This article endeavours to describe the XtaLAB Synergy diffractometer range and its capabilities.

In recent years, there has been an increasing demand for non-liquid nitrogen based cooling systems in thermal analysis because of environmental considerations and usability. Especially in differential scanning calorimetry (DSC), refrigerated cooling unit is often used. Using the Rigaku DSC, low temperature measurements from −90°C can be carried out. This indicates that refrigerated cooling can cover most DSC applications, and thus LN₂ cooling is only used for measuring a few limited materials.

Recently, Rigaku has developed the TMA8311/LR thermomechanical analyzer (TMA) with a refrigerated cooling unit. Previously, sub-ambient TMA measurement required LN₂ cooling, but the TMA8311/LR enables LN₂-free measurements thanks to the cooling system that achieves the lowest cooling temperature of −70°C, similar to the refrigerated cooling unit equipped DSC.