Effect of quenching and X-ray irradiation on the dielectric properties of PbI2 single crystals

The dielectric constant (K), loss (tan δ), and conductivity (σ) of PbI2 single crystals, after quenching and X-ray irradiation are measured in the frequency range 102 to 107 Hz and in the temperature region 30 to 300 °C. X-ray irradiation of as-grown crystals increases only the low frequency K and tan δ. Quenching (from 370 °C) and X-ray irradiation of these crystals produces the same effect; the changes in K and tan δ at room temperature (≈ 30 °C) are largest in the latter samples. K and tan δ of the samples subjected to different treatments (like quenching and X-ray irradiation) increase with temperature, the rate of increase is smaller at higher frequencies; the largest rate of increase is observed in quenched and X-ray irradiated samples. The plot, log δ versus 1/T for these samples give activation energies for conduction in the temperature region 200 to 280 °C as 0.44, 0.41, 0.39, and 0.35 eV for as-grown, quenched, X-ray irradiated and quenched, and X-ray irradiated PbI2 crystals, respectively. An attempt is made to understand these results.