The dielectric spectrum of europium doped CaF 2

Abstract

The complex dielectric constant has been measured at five audio frequencies (10 2–10 4 Hz) over the temperature range 4.2–400K for samples of europium-doped (nominal concentrations of 0.55% and 1.26%) CaF 2. Three strong relaxations are observed which indicates rather large amounts of the Eu 3+ ion. The three principal relaxations, which have activation energies of 0.413, 0.573 and 0.746 eV, are compared with previously observed dipolar complexes in rare-earth doped alkaline-earth fluorides. Of particular significance is the absence of strong, low-temperature relaxations which are often found in rare-earth doped alkaline-earth fluorides. Several weak relaxations are also observed.