Structure and dielectric characteristics of PbFe$_{0.5}$Nb$_{0.5}$O$_{3}$ single crystals grown under different conditions

The structure and dielectric and magnetic characteristics of plumbum ferroniobate crystals grown from a solution–melt containing potassium fluoride have been investigated. The obtained crystals have a cubic shape, 4-mm edges, and a rhombohedral structure at room temperature. Iron ions in the samples have the valence state of Fe$^{3+}$. A change in the Mössbauer spectra with a change in temperature has been registered; this is indicative of strong diffusion of the magnetic phase transition in the range from -130 to -230$^\circ$C, which is enhanced due to incorporation of fluorine atoms into the structure of the basic compound accompanying the synthesis process and clusterization of this structure. The latter phenomena also lead to a decrease in the temperature of transition from the ferro- to paraelectric phase.