Investigation of structural and dielectric characteristics of La-doped BZT ceramics

Abstract

Barium zirconium titanate (BZT) has garnered considerable interest due to its tunable dielectric and ferroelectric properties, making it suitable for memory devices and multilayer capacitors. This study investigates the impact of lanthanum (La) doping (2%, 4%, and 5%) on the structural, dielectric, and electrical properties of BZT ceramics synthesized via the sol–gel method. X-ray diffraction (XRD) confirmed a single-phase tetragonal perovskite structure (P4mm), with lattice contraction (c/a ratio decreasing from 1.0095 to 1.0092) due to La³⁺ substitution at the Ba²⁺ site. A secondary phase (La₂Ti₂O₇) emerged at higher doping levels, reducing tetragonality and grain size (from 497 nm for pure BZT to 238 nm for 5% La-doped BZT), as evidenced by FESEM. Dielectric studies revealed frequency dispersion, with ε′ decreasing from 74,600 (BZT) to 55,067 (5% La-doped BZT) at 100 Hz due to suppressed interfacial polarization. The permittivity stabilized to ~ 1,200–1,500 at 1 MHz across all compositions, reflecting dominant electronic polarization at higher frequencies. La doping reduced dielectric losses (tanδ) by 20–30% above 10 kHz, indicating improved high-frequency stability and a shift in Curie temperature (T_e) from 110 °C (BZT) to 120–121 °C (La-doped samples), attributed to altered ionic mobility. Impedance spectroscopy indicated a correlated barrier hopping (CBH) conduction mechanism, with activation energy decreasing from 0.052 eV (BZT) to 0.011–0.019 eV (La-doped samples), suggesting facilitated charge transport. Nyquist plots confirmed non-Debye relaxation, emphasizing the role of grain boundaries in conduction. This work demonstrates that La doping effectively tailors BZT’s functional properties, offering a pathway to optimize performance for high-frequency capacitive and energy storage applications. The findings provide new insights into defect-mediated property modulation in doped perovskites, distinguishing this study from prior literature through systematic quantification of La’s effects on lattice dynamics and conduction mechanisms.