Multifunctional properties of Mg-doped (Ba0.85Sr0.15)TiO3 ceramics: A combined structural, dielectric, electromechanical, and impedance analysis

Abstract

Ceramics based on Barium Strontium Magnesium Titanate ((Ba₀.₈₅Sr₀.₁₅)₁₋ₓMgₓTiO₃) were synthesized via the conventional sol-gel method, with different compositions (x = 0, 2, 4, 6, 8, and 12 mol.%). The resultant powders were calcined at 950°C for 4 hours to stabilize the phase formation. The X-ray diffraction (XRD) analysis, combined with Rietveld refinement using FullProf, verified that undoped samples exhibit a tetragonal structure belonging to the P4mm space group, whereas the incorporation of Mg led to the emergence of a hexagonal phase associated with the R-3 space group. Intermediate compositions exhibited a coexistence of tetragonal and hexagonal phases, without secondary phases. Fourier-transform infrared spectroscopy (FTIR) analysis identified distinctive absorption bands within the 450–600 cm⁻¹ range, attributed to the stretching and bending vibrations of TiO₆ octahedra. Scanning electron microscopy (SEM) images indicated improved densification and reduced grain size, with x = 6 mol.% showcasing a uniform grain distribution and higher density. The average particle size, estimated using Williamson-Hall plots, was found to be in the range of 125–140 nm with an uncertainty of approximately 5–10 %. Dielectric characterization across the frequency range of 1 kHz to 2 MHz demonstrated a diffuse phase transition, with the dielectric permittivity (εr) increasing significantly with Mg doping. Additionally, the dielectric response exhibited broad thermal stability, making these ceramics promising candidates for advanced microelectronic applications. Impedance spectroscopy showed a decrease in grain and grain boundary resistances with increasing Mg²⁺ content, along with an increase in capacitance values, indicating improved charge transport and interfacial polarization. The observed non-Debye relaxation and slight rise in activation energy confirm thermally activated conduction mechanisms influenced by Mg doping. This study highlights the impact of Mg incorporation on the electromechanical, structural, microstructural, and dielectric properties of ((Ba₀.₈₅Sr₀.₁₅)₁₋ₓMgₓTiO₃) ceramics, paving the way for advancements in multifunctional materials.