Interfacial Polarization and Electrical Conductivity in Sapphire

Dielectric relaxation effects, a dissipation factor peak, and both capacitance and conductivity dispersions were observed in pure and doped single crystals of Al 2 O 3 between 10 2 and 10 5 cps and between 700° and 1200°C. The observed peak heights and computed intrinsic relaxation times do not, in general, support a dipole rotation model. The observed behavior is interpreted instead as interfacial polarization in a layered di‐electric. The activation energies for conduction computed on the basis of this model were 2.4 ± 0.1 and 1.6 ± 0.2 ev.