Elastic Properties of Lithium Germanate Glasses Studied by Brillouin Scattering

概要

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To investigate the correlation between structural changes and physical properties, the elastic properties of lithium germanate glasses, $x$Li2O$\cdot$($100-x$)GeO2 represented as a function of Li2O mole fraction, have been studied in the composition range $6\leq x\leq 36$ mol % by Brillouin scattering spectroscopy. Raman spectra have also been measured to clarify the composition variation of structural changes. Several elastic properties, such as sound velocity and elastic modulus, have been determined from the Brillouin shift. The longitudinal and transverse sound velocities increase up to about $x=20$ mol %, and above $x=20$ mol %, they become nearly constant. Elastic moduli, such as longitudinal modulus ($L$) and shear modulus ($G$), increase gradually up to $x=22$ mol % and then decrease with a further increase in Li2O content. It is considered that such behaviors are due to the change in the coordination number of germanium atoms and the formation of nonbridging oxygen. Differently from other elastic moduli, Poisson’s ratio ($\sigma$) shows a similar behavior to sound velocity.
2010-07-25