The process of ionic segregation in the surface layer induced by the thermal treatment of the NaNbO₃ crystal was studied. The study of the as grown crystal and the crystal heated at 970 K in ambient air was carried out for comparison. The changes in the concentration of the elements within the surface layer were determined using XPS measurements. The AFM technique was applied to determine the surface morphology related to nano-scale transformation. The possibility of appearance of the Ruddlesden–Popper phases was detected by the XRD test. The change in the features of the electric permittivity, the loss tangent, and the electric conductivity was ascribed to the marked participation of the chemically modified surface layer in the measured effective electrical properties.

Fe-doped Bi₁₂MnO₂₀–BiMn₂O₅ ceramics was sintered at 1130 K for 6 h in ambient air. Two centro-symmetric phases formed thermodynamically stable self-composite material that was deduced from X-ray pattern analysis. The lattice parameters were a = 10.147(8) Å—for the cubic I23 Bi₁₂MnO₂₀ phase; and a = 7.545(4) Å, b = 8.538(1) Å, c = 5.758(3) Å—for the orthorhombic Pbam BiMn₂O₅ phase. The ⁵⁷Fe Mössbauer spectrum, recorded at room temperature, has shown pure electronic quadrupolar split. The major doublets reflected the occurrence of Fe³⁺ ions distributed in two sites, i.e., octahedral Fe⁴⁺O₆ and square pyramidal Fe³⁺O₅, with preferential occupation of the pyramidal sites, that was consistent with the Pbam phase symmetry. The third doublet resulted from the presence of iron Fe³⁺ in tetrahedral Fe³⁺O₄ coordination and corresponded to a small admixture of the I23 phase. The DC resistivity ρ_DC(T) dependence on temperature has shown thermally activated features, and the value of E_a,DC varied in the range of 0.22–0.37 eV. The electric impedance was measured in the f = 20 Hz–1 MHz and 100–690 K range. Two electrical relaxations were determined using the electric modulus formalism M″(T). Low-temperature relaxation has shown the temperature-dependent activation energy E_A,1 = 0.14–0.20 eV and characteristic time values of τ₀₁ = 10⁻¹⁰–10⁻¹² s in 100–200 K range. It was attributed to the charge transfer between Mn⁴⁺/Mn³⁺ sites. The other relaxation occurred in the 170–220 K range, and it exhibited the following values: τ₀₂ = 10⁻¹¹ s, and E_A,2 = 0.27 eV. A disorder-related VRH polaron model was proposed for ρ_DC(T) and for electric relaxation processes.

In our study BiMnO₃ ceramics has been sintered. The X-ray diffraction test has shown that the crystal lattice symmetry is monoclinic and centrosymmetric. Grain structure and stoichiometry has been determined by scanning electron microscopy whereas local disorder by X-ray photoemission spectroscopy. Leakage currents dominated the D–E hysteresis loop. Electric conductivity has been measured in the 85–770 K range. The studied fresh ceramics shows semiconductor properties. Charge-order transition occurrence has been deduced. The dc resistance switching occurs following the application of electroformation at a high temperature range. This effect is reversible, i.e. the R_dc(T) recovers semiconductor properties after thermal and electric field treatment.

The dynamics of electrical conduction relaxation has been studied for the disordered $\text{Pb}\left({\text{Mn}}_{1/3}{\text{Nb}}_{2/3}\right){\text{O}}_3$ ceramics. Broadband dielectric spectroscopy at frequency $f={10}^{–1}-{10}^7\text{Hz}$ was applied within the temperature range 173–473 K. The real ${\epsilon }^{\prime }$ and imagimary ${\epsilon }^{″}$ parts of complex dielectric permittivity at isothermal and isobaric thermodynamic conditions were measured. The hydrostatic pressure was changed up to 1.76 GPa. Two relaxation mechanisms were discerned. The isotherm has been fitted to activation law, $\tau \left(p\right)={\tau }_0\text{exp}\left[p\Delta V_a/R{T}_{\text{iso}}\right]$ above and below a crossover pressure $p_{\text{cr}}\approx 0.9\text{GPa}$. The temperature dependence of relaxation times scales to the thermally activated electric conductivity, $\sigma \left(0,T\right)\sim 1/{\tau }_m$ in the high-temperature range. The applied hydrostatic pressure decreased activation energies and stabilized the Fermi-glass features. The pressure effects have been discussed in framework of the Gate model, focused on the bivacancies’ role in the strain-related activation energy.