Several series of glasses with the general formula xR2O · (1 - x)R' O · P2O5 were prepared and the dielectric loss and internal friction data were taken. The dielectric losses of alkali metaphosphate glasses are greatly reduced by the substitution of alkaline-earth oxide for alkali oxide. Some of the investigated series show a weak minimum in the dielectric loss. The internal friction measurements reveal a high temperature peak, in addition to the single alkali peak and the intermediate temperature peak commonly observed in phosphate glasses. The origin of this high temperature peak is discussed.
van Ass, H. M. J. M., & Stevels, J. M. (1974). Internal friction and dielectric losses of mixed alkali-alkaline earth metaphosphate glasses. Journal of Non-Crystalline Solids, 16(2), 267-280. https://doi.org/10.1016/0022-3093(74)90130-6