Ceramics-Silikáty 57 (4) 290-296 (2013)

STRUCTURAL AND DIELECTRIC STUDIES ON Sr_0.5-3y/2La_yBa_0.5Nb₂O₆ CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

Sr_0.5Ba_0.5Nb₂O₆ (SBN50) ceramic doped with different concentration of Lanthanum, La according to stoichiometric formulation of Sr_0.5-3y/2La_yBa_0.5Nb₂O₆ (LSBN) with y = 0.01, 0.03, 0.05 and 0.07 prepared using traditional ceramic method at the calcination temperature of 1200°C and sintered at 1300°C at varied sintering time. The effects of the sintering time and La³⁺ substitution on the morphological, compositional, structural and electrical properties of the LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and dielectric analysis. The XRD spectra confirm the presence of TTB structure in the ceramics. The Curie temperature (Tc) of the ceramic identified from the dielectric studies performed in the temperature range of 28°C to 300°C. The temperature dependent dielectric exhibits broad peaks indicating a diffuse phase transition and relaxor behavior of the ceramic. The measured density of the samples is proportional to the sintering time and inversely proportional to the amount of the La³⁺ substitution. The solubility limit of La³⁺ ions in the SBN solid solution is at y ~ 0.05. This observation is also supported by the dielectric results where the dielectric properties of the ceramic deteriorate for y > 0.05 La substitution.

Keywords: Dielectric properties, Curie temperature, Microstructure, Density