Some Dielectric Properties of Tantalum Pentoxide

Abstract

The dielectric constant and dissipation factor of β- and α-Ta2O5 ceramics and of plates cut from a boule of α-Ta2O5 have been measured from 77° to 373° K over a frequency range from 100 cps to 100 kc/sec. β-Ta2O5 ceramics behave as typical dielectric materials. On the other hand, α-Ta2O5 ceramics exhibit large migrational losses, similar to those found in glasses, due to the migration of the tantalum ion through the structure. The activation energy Q of the process is estimated to be about 0.64 eV, in close agreement with 0.71 eV found from the formation of anodic films on tantalum. This and other facts suggest that anodic tantalum pentoxide is similar to that of the α form. A large relaxation peak is found in the data for boule α-Ta2O5 material having Q=0.2 ev and τ0=10—10 sec. This peak must arise from a large deformation of the structure to account for such a large relaxation time and large dielectric constant peak.