The enhancement mechanism of dielectric properties of Pb(Zr,Ti)O3 via (Mg2+,Sb3+) incorporation for supercapacitors

Due to the extraordinary versatility of the perovskite structure in accommodating different dopant ions in its structure, in recent years a huge number of multifunctional perovskite materials have been developed. In this work we aim to obtain high temperature-stable and huge dielectric constant materials for supercapacitors by doping divalent Mg²⁺ and trivalent Sb³⁺ ions into the octahedral sites, and divalent Sr²⁺ ions into the dodecahedral sites of lead zirconate-titanate perovskite. The resulting (Pb_0.95Sr_0.05)(Zr_0.425Ti_0.45Mg_0.042Sb_0.083)O_3-δ is examined by X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), dielectric spectroscopy (DS) and resonance dielectric spectroscopy (RDS) in order to correlate composition, local structure, ion valence and chemical environment of the doped material with the dielectric properties. HRTEM evidences that a composite structure, with co-existent ferroelectric domains and relaxor nanodomains, is formed by doping. XPS shows that Sb³⁺ and Mg²⁺ substitute for the Ti⁴⁺/Zr⁴⁺ ions, pointing to these strong defects as the main cause for the appearance of the relaxor phase. DS and RDS found that the ferroelectric lead zirconate-titanate transforms into a re-entrant relaxor-ferroelectric composite with a huge dielectric constant of about 10⁴ which remains stable (within ±10%) in the high temperature range up to 250 °C, pointing to this mechanism of relaxor phase re-entrance below the normal ferroelectric phase transition, as being responsible for the enhancement.