Study of the nature of defects and their effects on electrophysical parameters of solid solutions PZT doped with nickel and iron ions by using EPR

PZT material has piezoelectric properties, which appear due to the high dielectric constant, higher than the electromechanical coupling coefficient, and a significant spontaneous polarization. Lead zirconate titanate... [ view full abstract ]

PZT material has piezoelectric properties, which appear due to the high dielectric constant, higher than the electromechanical coupling coefficient, and a significant spontaneous polarization. Lead zirconate titanate Pb(Zr_1–xTi_x)O₃ (PZT) ceramics is important ferroelectric material which is applied in capacitors, memory cells (FeRAM), ultrasonic sensors, IR detectors, electro-optic devices etc.

The technology of the ceramic materials production is very complicated and small change in the technology may have a different effect on the synthesis of piezoelectric materials and the chemical reactions in them.

The PZT materials doped with nickel and iron with general chemical formula Pb_0.95Sr_0.05(Ti_0.475Zr_0.525)O₃ + xNiO + yFe₂O₃ + zPbO (x = 0, 0.033, 0.066, 0.1, 0.133 wt %; y = 0.1, 0.15 wt %; z = 0.05 wt %) were investigated in the present work. PZT materials were prepared by using conventional route. Studies by electron paramagnetic resonance (EPR), electron-microprobe analysis and analysis of electrophysical parameters were used for detection of correlation between intrinsic and impurity defects and electrophysical parameters of the investigated ceramics.

The effect of doping by Fe₂O₃ and NiO on structural and electrophysical properties is examined with different concentrations of dopants. We can assume that the partial substitution by Fe³⁺ and Ni³⁺ at A and B positions in perovskite lattice influence on the formation of an additional phases of PbNiO₃, PbFe₁₂O₁₉. These paramagnetic defects are associated with oxygen vacancies. Ni^{3 +} EPR signal is observed for the first time. All observed EPR lines depend on the oxygen vacancies concentration.