Effect of multi-component inorganic impurity K$_4$[Ru$_2$Cl$_{10}$O] on phase transition and dielectric properties of KDP crystal

Data have been obtained on the effect the addition of complex inorganic molecules K$_4$[Ru$_2$Cl$_{10}$O] produces on the dielectric properties and phase transition in KH$_2$PO$_4$ crystals (KDP). It is shown that selective penetration of the impurity in the prismatic growth sector {010} of the crystal causes a significant suppression of the domain contribution to the permittivity of this sector. The dielectric properties of the pyramidal sector {101} are virtually identical to the properties of a pure crystal. Measurements in the vicinity of the phase transition temperature have shown that the peak of $\varepsilon_c$ in an impurity-containing sector is shifted for 0.35 К to lower temperatures compared to a pure crystal.