Abstract
The attenuation of ultrasonic compressional waves in CoO-P2O5 glasses has been measured over the temperature and frequency ranges 250 to 640 K and 15 to 75 MHz, respectively. Twin loss peaks in the attenuation against temperature plots at constant frequency, were attributed to a relaxation loss of the standard linear solid type, with low dispersion and two, discrete, Arrhenius relaxation times. Unlike the case of low-temperature loss peaks in glasses, it was not found necessary to assume a continuum of relaxation times to explain the width of the loss peaks. Activation energies and attempt frequencies were in the range, respectively, almost one and three orders of magnitude higher than corresponding values typifying the low-temperature loss peaks in the same glass system. This result suggests the existence of 2-well systems with dimensions of the order of the diameter of a structural unit or atomic ring rather than the width of one or two atoms, and perhaps relaxing particles the size of a structural unit rather than a single oxygen atom. Activation energies in the various glasses were found to be proportional to the product of the mean force constant and compressibility. The calculated number of two-well systems (loss centres) per unit volume is small and comparable with what obtains in the low-temperature loss case. The composition dependence of several other properties of the relaxation process is discussed and a common feature is a discontinuity in the composition dependence of all of these properties at metaphosphate composition.
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Bridge, B., Higazy, A.A. Ultrasonic relaxation in CoO-P2O5 glasses at high temperatures. J Mater Sci 23, 438–450 (1988). https://doi.org/10.1007/BF01174668
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DOI: https://doi.org/10.1007/BF01174668