Structural, spectroscopic and dielectric properties of Ca-doped BaTiO3

Abstract

Ca-doped barium titanate BaTiO3 nanopowders were synthesized by the sol–gel process using barium acetate [Ba(CH3COO)2], calcium acetate [Ca(CH3COO)2] and titanium butoxide [Ti(OC4H9)4] as precursors. This method was adopted because it allows obtaining powders of high purity, chemical homogeneity and fine particle size, and crystallization is possible at very low temperatures (800 °C) compared to that used by the conventional solid-state reaction method. In this study, the characterization of nanopowders and ceramics using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), dielectric measurements, FTIR and Raman spectroscopy is carried out. The results revealed that the calcium ion incorporation had significant effect on structural and dielectric properties of barium titanate BaTiO3 (BT). XRD patterns suggested that nanopowders calcined at the temperature of 800 °C during 2 h could be crystallized into perovskite structure, with an average crystallite size in the range of 19.89–25.04 nm. Furthermore, it was observed that the Ca concentration variation affected the emission process with little displacement in the peak position. These results proved the optical band gap reduction by the presence of inter-band electron levels. Finally, the dielectric properties of the prepared samples were measured, revealing that the dielectric permittivity decreased with frequency increase, and the grain size and Curie temperature of the Ba1−xCaxTiO3 (BCT) ceramics sintered at 1200 °C were greatly affected by Ca substitution.