Strontium-induced phase transition and dielectric relaxation in PZT-AlSb ceramics

Lead zirconate titanate (PZT) ceramics remain central to high-performance piezoelectric and dielectric technologies. In this work, (Pb1-xSrx[(Zr0.52Ti0.43)(Al0.5Sb0.5)0.05]O3 (PZT-SAS) ceramics with SrO substitution levels x = 0.02, 0.04, 0.06, and 0.08 were synthesized via the solid-state reaction route to investigate the structural, microstructural, and dielectric responses arising from coupled Sr2+, Al3+/Sb5+ amphoteric co-doping. X-ray diffraction (XRD) analysis confirmed mixed tetragonal–rhombohedral phase coexistence across all compositions. Deconvolution of the (002)T/(200)T/(202)R reflections in the 42°–47° range showed systematic evolution of phase fractions, where the tetragonal content increased from ∼38 % at x = 0.02–∼57 % at x = 0.08. Fourier-transform infrared (FTIR) spectra exhibited a dominant M − O vibrational band at 530.5 cm−1, characteristic of BO6 octahedral bonding in perovskites. Microstructural analysis revealed significant grain coarsening with Sr addition: average grain size increased from ∼1.8 μm (x = 0.02) to ∼4.6 μm (x = 0.08), accompanied by improved densification, where the bulk density rose from 5.26 g/cm3 to 6.12 g/cm3. Impedance spectroscopy showed typical NTCR behavior, with decreasing Z′ and Z″ across 600–700 K, and Nyquist plots exhibited single depressed semicircles indicative of non-Debye relaxation dominated by grain and grain-boundary contributions. Increasing Sr content reduced grain-boundary resistance and shifted relaxation peaks toward higher frequencies. AC conductivity followed Jonscher's power law, showing a low-frequency σdc plateau and a high-frequency dispersion region attributed to hopping conduction of localized charge carriers. These findings demonstrate that Sr/PZT-SAS ceramics offer a promising pathway for developing high-performance dielectric materials with controlled phase composition, low loss, and improved conductivity behavior.