Effect of Calcination Temperature on the Microstructures of Barium Titanate Hafnate Nanopowders Prepared by the Sol-gel Process

Abstract

Barium titanate hafnate (BaHf 0.1 Ti 0.9 O 3 , short for BHT) powders were prepared by sol-gel process at different calcination temperatures. Thermal analyses (TG-DTA), xray diffraction (XRD) and transmission electron microscopy (TEM) were performed. It is found that there are no exothermic peaks or endothermic vales above 700 • C in correspondence with new reactions. Therefore, the calcination temperature should be higher than 700 • C to facilitate the formation of BHT. The XRD spectra suggest that the powders possess perovskite structure without impurity. When the calcination temperature increased from 700 to 900 • C, the reflection peaks became sharper and stronger. The XRD and TEM results reveal that the average size of powder increases with the increasing calcination temperature.