Use of high temperature X-ray diffraction and pair distribution function for the study of carbonation characteristics of Barium Titanate at nanoscale

Barium titanate (BT) is extensively used in electronic industries for its high dielectric constant. However, the dielectric properties of BT significantly change due to carbonation at nanoscale. Commercially available tetragonal BT powder was milled to study the local atomic distribution and phase transformation behaviour with temperature. Nano BT powder was prepared by the high energy ball milling (90 h) from its bulk counterpart. It was carbonated when it was exposed to open atmosphere. The milled BT sample was characterised by high temperature X-ray diffraction (HT-XRD), pair distribution function (PDF) and transmission electron microscope (TEM). Local atomic distribution was obtained from PDF analysis. The peak due to C-O and Ba-C pair distance were observed from PDF for 90 h milled carbonated BT. TEM analysis revealed that particle diameter was in the range of 15-50 nm. How the phase of nano BT ceramics transformed with temperature was strudied. It was observed that orthorhombic BT transformed into tetragonal and cubic phase via the monoclinic phase during heating at 900 degrees C. Coexistence of multi phases of BT was also observed from HT-XRD. BaCO3 disappeared at high temperature.