Dielectric and conductivity behavior of Mn-doped K0.5Na0.5NbO3 single crystal

Dielectric and conduction behaviors of [001]-oriented K0.5Na0.5Nb0.5O3 single crystal (KNN) and 0.5 at% Mn-doped KNN single crystal (KNN-Mn) have been investigated in a broad temperature range. At low temperatures (330-400 K), an observed slight decrease of conductivity could be connected with the decreases of hole carrier concentration and mobility for the KNN-Mn. At high temperatures (723-773 K) above Cure temperature, the dielectric relaxation and conduction behavior of the samples were analyzed by measurements of impedance spectroscopy and universal dielectric response law. The activation energy values for relaxation frequency and conduction were ~ 0.97 eV and 0.60 eV for the KNN-Mn, respectively. They could be attributed to the thermal motion of double ionized oxygen vacancies and the formation of defect dipoles. The defect compensation mechanism was proposed based on Mn4+ ion substitution. The KNN-Mn promoted a higher concentration of oxygen vacancies compared with KNN crystal, which gave rise to smaller domain size and higher piezoelectric properties.