AsianScientist (Sep. 8, 2017) – In a study published in the journal Science Advances, researchers in Japan describe a holographic technique to create three-dimensional (3D) representations of the atomic structures.
People usually associate holograms with futuristic 3D display technologies, but in reality, holographic technologies are now being used to help study materials at the atomic level. X-rays, a high energy form of light, are often used to study atomic structure. However, X-rays are only sensitive to the number of electrons associated with an atom. This limits the use of X-rays for studying materials made up of lighter elements.
Neutron measurements can often fill in the gaps in structures when X-ray measurements fail, but neutron beams are harder to make and have lower intensities than X-ray beams, which limits their versatility.
In this study, a collaboration among researchers working at national particle accelerator facilities across Japan has produced a new multiple-wavelength neutron holography technique that can give insights into previously unknown structures.
They demonstrated their neutron holographic method using a europium (Eu)-doped calcium fluoride (CaF2) single crystal and obtained clear 3D atomic images around trivalent Eu-substituted divalent Ca, revealing never-before-seen intensity features of the local structure that allows it to maintain charge neutrality.
“We knew that neutron holography might be able to tell us more about the structure of a europium-doped calcium fluoride crystal,” said lead author Professor Kouichi Hayashi.
“Europium ions add extra positive charge to the crystal structure, and our neutron holograms showed how fluorine atoms arranged in the lattice to balance this excess charge. These kinds of structural problems are often encountered by materials scientists developing new electronic materials, and our method offers an exciting new tool for these researchers.”
The new holographic method works by firing neutrons with controlled speed at a sample, which, in this case, is the europium-doped calcium fluoride crystals. Neutrons are normally thought of as particles, but they also possess wave-like properties similar to light, depending on their speed.
When the neutrons hit europium atoms, gamma rays are produced in a pattern controlled by the local structure. The gamma ray patterns, or holograms, measured from neutrons travelling at different speeds are combined to produce a 3D representation of the europium atoms in the crystal.
“Neutron sources are less intense than X-ray sources, but it is essential that we work around this issue to develop more effective methods for exploring structures with light elements. Our work here represents a step towards a full toolbox of complementary X-ray and neutron techniques for materials research,” said Hayashi.
The article can be found at: Hayashi et al. (2017) Multiple-wavelength Neutron Holography with Pulsed Neutrons.
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Source: Nagoya Institute of Technology; Photo: Shutterstock.
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