COMPLEX ADMITTANCE STUDY OF POTASSIUM YTTRIUM FLUORIDE

The complex admittance of pure and 0.5 mol% sodium doped potassium ytt rium fluoride polycrystalline pellets, between two inert blocking elec trodes, was studied from 300 to 950 K in the frequency range 50-100 kH z. In most cases the admittance plot exhibited a depressed circular ar e in the low frequency region and a straight line in the high frequenc y region. The bulk conductivity sigma the dielectric constant epsilon' and the loss angle tan delta were determined from the admittance plot s. The high values of epsilon' observed at high temperatures were attr ibuted to space charge polarization effects. The a.c. conductivity was found to increase with increasing frequency.