KTiOPO₄ crystals, both pure and doped with rubidium Rb⁺ and fluorine F^– ions, were grown in temperature range from 1060 to 846°С from salt solvent containing potassium metaphosphate ₃ and potassium orthophosphate К3РО₄ by using a Czochralski modified method. Potassium–sodium titanyl phosphate crystals were obtained from KTiOPO₄ crystals by the potassium isomorphic replacement with sodium; to this purpose, sodium chemical diffusion from NaNO₃ melt was used. Their ionic conductivity was studied by the electrochemical impedance spectroscopy method. The KTiOPO₄ crystal doping with rubidium and sodium ions was shown to lower the conductivity, whereas the doping with fluorine ions results in increased conductivity.