Dielectric relaxation in yttrium- and lanthanum-doped calcium fluoride

Abstract

The complex dielectric constant has been measured at five audio frequencies over the temperature range 5.5-400 K for 0.1 mol% of yttrium and lanthanum in calcium fluoride. Five relaxations are observed in the yttrium-doped material and one is observed for lanthanum. These results are consistent with trends with ion size observed previously for rare earths in calcium fluoride and emphasize that ion size is the primary factor determining defect formation in calcium fluoride doped with trivalent ions.