Funct. Mater. 2023; 30 (4): 471-477.
Origin of non-monotonic behaviour of electrical conductivity of potassium dihydrophosphate crystals depending on gamma-irradiation dose
1V. N. Karazin Kharkiv National University, 4 Svobody Sq., 61022, Kharkiv, Ukraine
2Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Nauky Ave., 61001 Kharkiv, Ukraine
Investigated is the dependence of dc conductivity of undoped KDP crystals on the dose of gamma-irradiation and the temperature. At room temperature the value of conductivity changes non-monotonically with the dose of gamma-irradiation. At low irradiation doses it exponentially decreases as the irradiation dose rises. Then, after reaching the minimum at 1.2⋅103 Gy dose, the conductivity increases with further irradiation up to 2.0·104 Gy proportionally to the dose. The temperature dependences of the conductivity are measured in 15÷133 °С range. It is established that they obey the exponential law and are described by the Arrhenius relation. There are determined the conductivity parameters such as the activation energies and the pre-exponential factors. The analysis of the obtained results shows that at room temperature the non-monotonic dependence of electrical conductivity at gamma-irradiation is mainly bound up with the competition of two mechanisms of charge transfer: migration of proton vacancies and migration of protons along the interstices. The intrinsic mechanism related to the processes of thermal generation and migration of charge carriers dominates at temperatures above 85°С. The concentration of proton vacancies is determined, and its dependence on the gamma-irradiation dose is established.
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