Dielectric characteristics of HoFeO3 crystals and their modification on SHI irradiation

Results on dielectric properties of flux grown HoFeO3 crystals and their modification on irradiation with 50 MeV Li3+ ion beam are reported. The dielectric constant (epsilon'), dielectric loss (tan delta) and conductivity (sigma) as a function of frequency of the applied ac field in the range 1 kHz-10 MHz and at temperatures ranging from 30 to 550 degrees C are analyzed for the unirradiated and irradiated crystals. The value of epsilon' decreases with frequency for all the temperatures. The rate at which epsilon' falls with increase in frequency (1 kHz - 1 MHz) at each temperature in the range of 30-250 degrees C gets drastically reduced on irradiation of crystals with SHI. The peak value of dielectric constant depends on temperature and frequency. The relaxor type behaviour is observed for both unirradiated (UIR) and irradiated (IR) crystals with a shift in the peak temperature of irradiated crystal towards higher temperature for all frequencies. The relaxor character of HoFeO3 is strengthened on irradiation. This relaxor type behaviour is further elaborated using the theoretical fitting. The differences in the conductivity and activation energy for UIR and IR crystals are given. It is shown that irradiation affects the values of activation energies at all the frequencies in the range of 1 kHz-10 MHz. (c) 2005 Elsevier B.V. All rights reserved.