"This work shows that, even with a very low degree of order, at synchrotrons like the National Synchrotron Light Source at Brookhaven we can determine nanoscale structures using the right techniques," said Thomas Vogt, a Brookhaven physicist. "And with structural understanding we can start to predict properties and perhaps begin to manipulate them for useful applications."
Traditional X-ray powder-diffraction techniques rely on the long-range order in crystals to produce sharp "Bragg peaks" in a diffraction pattern. By examining these Bragg peaks, which result from X-ray scattering, scientists can determine the material's atomic structure.
But nanocrystals lack long-range order and often incorporate a large number of defects. As a result, their diffraction patterns are much more diffuse with few, if any, Bragg peaks. "This poses a real challenge to the traditional techniques for structure determination," explained Valeri Petkov of Michigan State.
To overcome the problem, the scientists used the "atomic pair distribution function technique" to read between the Bragg peaks of data produced by traditional X-ray powder-diffraction methods at Brookhaven's National Synchrotron Light Source.
In this way, the team proved that caesium can be intercalated in the nano-sized pores of a silicon-oxide zeolite in the form of positively charged caesium ions arranged in short-range order zigzag chains. The scientists say this verifies that CsxSi32O64 is a room-temperature stable inorganic electride.
"Electrides are novel materials that are just beginning to be studied," added Petkov. The compounds have potential for use as reducing materials in synthesis, and have interesting electronic properties such as low-energy electron emission.
The researchers reported their work in Physical Review Letters.