Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

Abstract

The complex dielectric constant, , of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε′′(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε′(ν) increases only at high temperatures; there is almost no change of ε′(ν) below 200 K. Both values of ε′ and ε′′ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.