Volume 27(2) - Summer 2011

A ribosome is a vast assembly consisting of proteins and RNAs. The molecular mass adds up to approximately 2.5 MDa, and it is the largest asymmetric entity whose structure has been solved in human history. The first step of X-ray structure analysis is to acquire wellordered crystals of the target material. Generally speaking, crystallization becomes more difficult as the size of the molecule increases. After this obstacle is overcome, one would then face the phase problem, a principle problem in crystallography. For such a huge complex, conventional phasing methods such as MAD and MIR may not work. Taking all of these issues into account, one can readily imagine that the structure determination of the ribosome must have been an extremely difficult task.

The 2009 Nobel Prize in Chemistry was awarded to those researchers who determined ribosome structures, not only because of the difficulty of the structure determination but also because the resultant structure answered many biological questions—such as underlying chemistry in protein synthesis—and is providing the basis for new drug discovery. Only X-ray structure analysis can yield the atomic structure of such an enormous complex.
 

Since crystal orientation and the degree of preferred orientation in thin films have a great influence on the properties of thin film devices, it is crucial for thin film devices to control the preferred orientation texture of thin film materials for applications such as light-emitting devices, ferroelectric memory and transparent conductive film applications, etc.

The Electron Back Scatter Diffraction (EBSD) technique, combined with a Scanning Electron Microscope (SEM), has been a popular approach for determining crystallite orientation and distribution in the field of material science. Recently, this technique has become focused of great interest due to major improvements in the throughput speed of analysis, as well as its capability for inspections to the scale down to several tens to hundreds of nm.

On the other hand, the irradiation area on the sample surface in pole figure (PF) measurements with X-ray Diffraction (XRD) is φ 10 μm to 50 mm. The advantages of PF measurements by XRD are as follows: firstly, it allows the analysis of textural information of samples averaged over a large area/volume and, secondly, this measurement can be performed under ambient conditions or at high/low temperature by changing the atmospheric conditions.

In the process of texture analysis of materials, it is necessary to express the distribution of crystallite lattices in the coordinates of the external field, such as applied stress, magnetic field, etc. For most thin film cases, it would be the lattice of a single crystalline substrate.

In earlier articles in this series about thin-film analysis techniques, out-of-plane measurement and in-plane measurement techniques were explained in the 2nd and 4th articles. This article will explain the basics of the pole figure measurement/analysis technique using out-of-plane and in-plane measurement geometry, followed by their applications for thin films samples.
 

X-ray diffractometry is a well-known method for analyzing samples of several tens of milligrams or more in weight or several millimeters or more in particle size.  It is used to identify substances in a sample and to analyze crystal quality, crystal orientation, and residual stress. Recently, new requirements of the technology have arisen. These include the identification of substances present in trace amounts (less than 0.1 mg) resulting from multiple synthesis processes, identification of foreign substances or deposits of 100 m m or less in size, and microanalysis of orientation and stress in welded parts and deformation-processed areas.  For these experiments, point detectors (i.e., scintillation counters) require long measurement times because of their low sensitivity coupled with the small signal. In some situations, an incorrect diffraction intensity ratio, resulting from the effect of coarse grains or particles, can make identification difficult. Combining a highintensity X-ray source and a two-dimensional detector provides the increased diffracted X-ray intensity and detection sensitivity needed for rapid analysis, even for extremely small samples or sample analysis areas.

This report primarily discusses the use of the latest X-ray diffractometer to analyze trace substances and micro areas. It also discusses specific applications.
 

Molecular structure determination has an important role both in fundamental science and applied sciences such as organic chemistry, inorganic chemistry, biochemistry, drug discovery, material chemistry, etc.  A number of analytical methods are routinely used to determine molecular structure: nuclear magnetic resonance (NMR), mass spectrometry (MS), infrared absorption spectroscopy (IR), X-ray diffractometry (XRD), and so on. In particular, single-crystal X-ray structure analysis is the most effective method of obtaining a detailed and overall three-dimensional structure of a molecule.

However, one critical problem is that single-crystal X-ray analysis cannot be performed if the target sample doesn’t form a single crystal. Even if the target sample crystallizes, it sometimes turns out to be twinned or a polycrystal.
 

The newly-released sequential general-purpose wavelength-dispersive X-ray fluorescence spectrometer, ZSX Primus III+ is the latest member of the ZSX Primus series. The ZSX Primus III+ with tube-above optics, a design based on the high-end ZSX Primus II system, has selected functions focused on daily routine analysis. The advantages of the ZSX Primus III+ are as follows:

• Optimized for powder analysis with features such as tube-above optics
• High-precision analysis of major components in alloys and oxides
• Improvement in trace element analysis
• Easy operation using “EZ Analysis” window
• Software support for advanced analysis methods
• Advanced software—new SQX program
• Energy- and space-saving design
   

Lithium ion secondary batteries (LIBs) are widely used in compact mobile devices such as cell phones and notebook PCs. Current research and development at universities, research institutions, and companies seek to create LIBs for use in large machines, including electric vehicles. Meanwhile, competition in the development of LIBs has intensified in Asian and Western countries.

Commercializing LIBs requires improvements in capacity, stability, and longevity, which in turn entail various assessments and evaluations. Figure 1 shows aspects of LIBs that equipment manufactured and sold by Rigaku can be used to assess. Among the evaluation methods currently available, X-ray diffractometry offers a wide range of analytical capabilities that allows extensive examination of structural changes in electrode materials, such as qualitative analysis, crystallite size analysis, and Rietveld analysis.

At the 50th Battery Symposium in Japan, held in 2009, half a dozen reports were presented on in situ measurements of LIBs by various analytical methods. In contrast, at the 51st Battery Symposium in Japan, held in November 2010 in Nagoya, the number of reports on in situ measurements of LIBs numbered 18, a threefold increase. Announced at this most recent symposium were the results of experiments done at SPring-8. The results of measurements of structural changes obtained with X-ray diffractometers while batteries are charged and discharged point to structural changes in electrode materials, even during the initial charge/discharge cycle; lithium desorption and insertion at certain points during the charge/discharge cycle; and other details, such as changes in bond distances between metal and oxygen atoms. Additionally, much work related to in situ evaluations is being done today in laboratory environments.  The results of laboratory analyses using the battery cell attachment discussed in this paper have been reported at the 78th Meeting of the Electrochemical Society of Japan(1) in March 2011.