Synthesis and Characterization of BaTiO3 Prepared by Molten Salt Synthesis Method

Abstract

The study first optimized the different processing parameters e.g. salt systems, heat treatment temperature, holding time. By NaOH-KOH based salt system phase pure powder can be prepared at 175oC. NaCl-KCl based system produced phase pure powder at 700oC. LiCl-KCl based system failed to produce phase pure BaTiO3 powder. Crystallite size of the synthesized powder found to be varying 30-43 nm depending on the processing time and temperature. TEM analysis revealed that particle size in the range of 70-100 nm. It has been observed that NaOH-KOH system synthesized powder can be densified (98%) at a temperature 1225oC. Interestingly ultrafine grain size (200-500 nm) retained in highly dense sintered sample. In case of NaCl-KCl based powder only 91% density achieved, microstructure shows significant amount of porosity. Dielectric constant and loss factor of the sintered samples (εr =1400 and tanδ = 2% at 1 kHz) are on a par with BaTiO3 prepared via conventional sintered sample. NaOH-KOH salt based prepared sample showed almost flatten Curie peak and NaCl-KCl salt system prepared sample showed broad Curie peak with a Curie temperature of 115oC. The peak shift and broadening can be explained qualitatively from temperature dependence of volume fraction between surface cubic layer, bulk tetragonal layer, and gradient-lattice-strain layer (GLSL).