EFFECT ON DIELECTRIC PROPERTIES OF A-SITE DOPING OF (BA₁₋₂ₓNAₓALₓTIO₃) CERAMICS

Abstract

The paper examines structural and dielectric properties of A-site Na + and Al + co-doped barium titanate ceramics (Ba₁₋₂ₓNaₓAlₓTiO₃) prepared by the solid-state reaction process, with compositions of x = 0.03 and x = 0.04. Materials were then allowed to be heated to 1150 0 C and sintered at 1350 0 C over 2 hours when analyzing the influence of co-doping on the formation of phases, microstructure, and dielectric performance. X-ray diffraction (XRD) was used to confirm that both compositions had a tetragonal perovskite structure, with small volumes of secondary phases to higher levels of doping being composed of Ba 2 TiO4. When the NaAl replacements were further increased, lattices became smaller and c/a ratio decreased, which shows a progressive change towards pseudo-cubic symmetry. Scanning Electron Microscopy (SEM) showed that the densification and grain growth were improved and its average size of the grains (x) was improved to 1625 than 2.824 00:24 to 8588 00:40, which corresponds to an augmented relative density (8588 00:24). Dielectric characterization in the frequency range of 1 kHz-1 MHz and temperature range of 25-150 C revealed that dielectric constant (ε 7 ) decreased significantly with an increase in dopant concentration, and dielectric loss (tan 7 ) increased. The greatest ε n 7 value of 46 (at 1 kHz) in the case of x = 0.03 dropped to 13 in the case of x = 0.04, and tan 7 went up to 1.0. The Curie temperature (T C ) changed marginally to 130 O C 127 O C showing the change of ferroelectric-paraelectric transition phenomenon. The current destruction of dielectric functionality has been associated with the creation of vacancies in the oxygen sites, defect dipole, and local lattice strain due to the aliovalent substitution of Na + and Al +alt Ba + position. These defects block the motion of domain walls and inhibit long-range polarization, moving the system to an relaxor-like dielectric behavior. The findings prove that NaAl co-doping is appropriate to increase densification, but it decreases the dielectric properties, indicating that such dual substitution is not appropriate to improve permittivity but can be useful to investigate charge compensation and defect interactions throughout lead-free BaTiO 3 ceramics.