This investigation was undertaken to study the process of sodium diffusion in single crystals of the metallic sodium tungsten bronze. Concentration gradients were established by effusion of sodium from single crystals into a vacuum. The concentration gradients were measured by means of an X-ray determination of a precision lattice constant, subsequently making use of the Vegard's law relationship to evaluate the sodium concentration. Advantage was taken of the high absorption of copper x-radiation in the sodium tungsten bronze in order to measure the lattice parameter of an exposed crystal surface.
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