Relaxation dynamics, phase pattern in the vicinity of the Curie temperature, Fe valent state and the Mössbauer effect in PFN ceramics

High-density lead ferroniobate, PbFe1/2Nb1/2O3 (PFN), was prepared by the conventional ceramic technology. Its dielectric properties, phase pattern in the vicinity of transition into the polar phase, and the x-ray electron and Mössbauer spectra were studied. The relaxation dynamics discovered at the temperature exceeding the Curie temperature at the frequencies of 3×10−2–105 Hz is described in detail. Near TC, the following sequence of phase transitions was established: rhombohedral (T<368 K)→pseudocubic (368 K387 K). It is shown that in both the ferroelectric and paraelectric phases the Fe ions are, mainly, in a high-spin valent state Fe3+ in the octahedral environment.