Electrical Properties and Internal Friction in Borophosphate Glasses Containing Alkali Metal Oxide

Abstract

The internal friction, dynamic modulus of elastically (G′), D. C. conductivity and dielectric properties in the glasses of 30 R2O-xB2O3-(70-x)P2O5 (R=Li, Na, K: x=0-70mol%) system were measured. The temperature dependence of D. C. conductivity in 30 R2O-xB2O3-(70-x)P2O5 system was described by the Rasch-Hinrichsen equation: σ=σ0exp(-ΔHdc/RT). The D. C. conductivity curve showed a maximum with a minimum activation energy at x=35mol% when the same alkali oxide is contained. The D. C. conductivity was largest for Li followed by Na and then by K for a mixed borate content. The activation energy was smallest for K followed by Na and Li. The frequency at which the peak of dielectric loss appeared was lowest and increased for Na and K in the order started. The activation energy of dielectric loss was nearly equal to that of the D. C. conductivity. One or two internal friction peaks were obserbed in the temperature range from -100° to 350°C at about 1Hz. The peak at lower temperature was due to the motion of alkali ions, because the activation and the peak temperature changed with x in a way similar to those in the D. C. conductivity and dielectric loss. On the other hand, the peak at higher temperature was due to migration of non-bridging oxygen. The dynamic modulus of elasticity (G′) on internal friction was calculated by considering the shape factor. G′s in glasses of 30 Na2O-xB2O3-(70-x)P2O5 were 1.5 to 4.0GPa in the range x=0 to 70mol%. G′s showed a maximum at x=35mol%. It was considered that BPO4 unit analogous to SiO2 were produced in the glass network.