Dielectric relaxation in flux grown KTiOPO4 and isomorphic crystals

Dielectric spectroscopy and dc conductivity have been studied in KTiOPO4 and isomorphic crystals in a temperature range 150–400 K. The experimental data indicate two temperature regions related to different types of relaxation processes. Alternation of the activation energy, suppression of the dielectric dispersion, and decreasing dissipation factor by three orders of magnitude has shown that the superionic state in KTiOPO4 and its isomorphs transit gradually to the dielectric state with temperature lowering. The transition leads to variation of transport properties from ionic to electronic conductivity. It was found that the parameters of the relaxation process (activation energy in the superionic state, temperature range of transition from ionic to electron conductivity) are determined by the sort of mobile cations. The temperature dependence of conductivity relaxation time was obtained from the electric modulus plots.