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Published online by Cambridge University Press: 10 February 2011
Information about the spatial distribution of sodium cations in sodium tellurite glasses is obtained from the decay rate of sodium spin echoes. The spin echoes decay due to the magnetic dipole coupling between sodium nuclei, with each pair contributing to the rate in proportion to 1/r6, where r is the distance between the pair. The experiment is used to probe the sodium distributions in sodium tellurite glasses as a function of sodium oxide content, and the resulting distance distributions are interpreted by comparison with model distributions. At low sodium contents the distribution is similar to that of a random model in which the sodium ions are constrained to be no closer than a minimum cut-off distance. At higher contents the distributions deviate significantly from the random model, suggesting the onset of medium range order in the distribution of sodium ions. This order is most pronounced at 20% sodium oxide content, the composition at which this glass has been claimed to have maximum stability against devitrification.