Synthesis conditions induced disorder and its role in affecting structural, dielectric, piezoelectric, optical behavior and enhancing energy storage efficiency in (Ba(1-x)Cax)TiO3 ceramics

Abstract

We examined the effect of Ca2+ substitution on the structural, dielectric, ferroelectric, piezoelectric, and optical properties of Barium Titanate (BT) prepared via the solid-state reaction route assisted with a heating cycle. X-ray diffraction (XRD) patterns confirmed the formation of single-phase perovskite structures for Ba1-xCaxTiO3, 0 <= x <= 0.08. Raman spectroscopy of the Ca2+ doped BT was in good agreement with the XRD data. Structural analysis revealed an increase in average grain size with the increase in Ca2+ concentration in BT except for BCT-5 (x = 0.05) whose average grain size decreased. The Curie temperature shifted towards a higher temperature with the increase in Ca2+ concentration in BT, which is consistent with the literature when Ca2+ goes into the Ba2+ site. For BCT-5, the decrease in average grain size and the increase in diffuseness parameter to 1.51 confirmed partial substitution of Ca2+ at Ti4+-site, generating oxygen vacancies that inhibited grain growth during the synthesis procedure. The recoverable energy density calculated from the PE hysteresis loop showed maximum value for BCT-3 = 224.3 mJ/cm(3) with a storage efficiency of 85%. The energy storage efficiency was greater than 80% for all the compositions, making them suitable for high energy density capacitors. The piezoelectric charge coefficient increased linearly with Ca2+ concentration except for BCT-5, due to partial substitution of Ca2+ at the Ti4+ site. The indirect optical bandgap varied from 1.97 eV to 2.24 eV with Ca2+ concentration associated with the combined effect of lattice disorder and defects, which can have applications in optoelectronics. Partial substitution of Ca2+ at the Ti4+ site decreased the optical bandgap of BCT-5.