Dielectric properties of quenched and laser-excited or field-treated LiF single crystals irradiated with X-rays
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Frequency and temperature dependences of dielectric constant, K, and loss, tan δ, and hence a.c. conductivity, σ, have been studied for LiF single crystals under a combination of treatments such as quenching, laser excitation, a.c. field treatment and X-ray irradiation. The measurements were made in the frequency range 102–107 Hz and in the temperature range 30–400 °C. The dielectric constant, K, of LiF at 30 °C was found to be 8.4 and to be independent of frequency, while the dielectric loss, tan δ, was below 10−3 at 102 Hz. The results indicate that the different treatments on LiF single crystals increase the room-temperature and also high-temperature K and tan δ values appreciably in the low-frequency region. Log σ versus 1/T plots at frequency 102 Hz give the activation energy for conduction in the intrinsic region as 0.97 eV for as-cleaved LiF; this value was found to decrease in variously treated LiF samples. The different treatments on LiF help to increase the concentration of charged lattice defects which, in turn, increases the K and tan δ values.
KeywordsPolymer Activation Energy Dielectric Constant Dielectric Property Dielectric Loss
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