Low frequency polarization effects in thin evaporated dielectric films

Dielectric measurements at frequencies between 0·01 c/s and 1000 c/s were made on vacuum deposited films of LiBr, LiI, LiF and cryolite. Large loss peaks and capacitance values up to 40 µF/cm2 were recorded, resembling previous results on NaCl and NaBr. The frequency dependence was however markedly different, in accordance with the high cation mobilities, in LiBr and LiI. The incremental capacitance in LiF followed an inverse square dependence on film thickness, and the loss peak frequency in LiBr and LiI was qualitatively related to excess vacancy concentration. Cryolite films had interesting high capacitance, low loss properties at raised temperatures. The results are discussed in relation to theories of electrode blocking polarization.