Effect of fluxing additive on sintering temperature, microstructure and properties of BaTiO ₃

Various fluxing materials are added to technical ceramics in an attempt to lower their sintering temperatures and make their processing economical. The effect of 0·3wt%Li ₂CO ₃ addition on the phase, microstructure, phase transition temperatures and dielectric properties of BaTiO ₃ was investigated in the present study. The addition of 0·3wt% Li ₂CO ₃ was observed to lower the optimum sintering temperature by ∼200°C with no second phase formation and cause a five-fold reduction in grain size. Rhombohedral-to-orthorhombic and tetragonal-to-cubic phase transitions at the expected temperatures were evident from the Raman spectra, but the orthorhombic-totetragonal phase transition was not clearly discernible. The persistence of various phase(s) at higher temperatures in the flux-added materials indicated that the phase transitions occurred relatively slowly. A decrease in dielectric constant of Li ₂O-added BaTiO ₃ in comparison to pure BaTiO ₃ may be due to the diminished dielectric polarizability of Li ⁺ in comparison to Ba ²⁺.