Dielectric properties of NaF-B2O3 glasses doped with certain transition metal ions

Dielectric constant epsilon, loss tan delta a.c. conductivity sigma and die lectric breakdown strength of NaF-B2O3 glasses doped with certain transitio n metal ions (viz. Cu2+, VO2+, Ti4+ and Mn4+) are studied in the frequency range 10(2)-10(7) Hz and in the temperature range 30-250 degrees C. The val ues of epsilon, tan delta sigma(a.c.) are found to be the highest for Cu2doped glasses and the lowest for Mn4+ doped glasses. Activation energy for a.c. conduction and the value of dielectric breakdown strength are found to be the lowest for Cu2+ doped glasses and the highest for Mn4+ doped glasse s. With the help of infrared spectra, increase in the values of epsilon and tan delta of these glasses with frequency and temperature are identified w ith space charge polarization. An attempt has been made to explain a.c. con duction phenomenon on the basis of quantum mechanical tunneling model (QMT) /carrier barrier hopping model.