Origin of enhanced dielectric and multiferroic properties in Pb-doped BaTiO3 ceramics

The ferroelectric and ferromagnetic properties of bare BaTiO3 are weaker than the PbTiO3, which limits its magnetoelectric applications. To overcome these problems, a small amount of Pb was doped in BaTiO3 via a solid-state reaction route to improve the multiferroic properties of the compound. In this way, the modified single-phase Ba1-xPbxTiO3 (0 ≤ x ≤ 0.075) samples have demonstrated improved characteristics and desirable application in the area of microwave tunable devices and multi-layered ceramics capacitors. Rietveld refinement technique ensures that the samples retain their parent perovskite tetragonal phase in P4mm space group. The presence of the metal oxide and several bands were finalized through the Fourier transform infrared (FTIR) spectroscopy study. The elemental composition and the oxygen vacancies were confirmed by the X-ray photoelectron spectroscopy (XPS) studies suggesting two valence states, i.e., Ti3+ and Ti4+ of titanium, in both undoped and doped samples. In addition, XPS spectra also confirm that the Pb-doped BaTiO3 samples are less defective than the undoped ones. The Raman spectra reveal the distorted tetragonal perovskite structure of the samples in the P4mm space group by confirming the four fundamental Raman modes. The dielectric studies in the frequency range of 50 Hz to 5 MHz at room temperature reveal an increase in dielectric constant on Pb doping at the Ba site. The dielectric data analyzed in the framework of the universal dielectric response (UDR) model exhibit no deviation from linear behavior. The a.c. conductivity is found to enhance with the increase in Pb content due to the small polaron hopping conduction mechanism between the Pb and Ba ions. The field-dependent magnetization suggests the diamagnetic nature of the undoped BaTiO3 sample and feeble ferromagnetism in the doped samples. Ferroelectric hysteresis loops reveal linearly raised polarization parameters on Pb content. The existence of both ferromagnetic and ferroelectric phenomena confirms the multiferroic nature of Pb doped BaTiO3 system at room temperature.