Dielectric properties of barium titanium ceramics doped by lanthanum oxide.

The method of oxalate co-precipitation assisted with microwave is used for the synthesis of pure barium titanate (BT) particle with a diameter of 30-50nm by choosing tetrabutyl titanate Ti(OC4H9)4 (98.0%), barium nitrate Ba(NO3)2 (99.5%), oxalate H2C2O4 (99.5% purity) and nitric acid HNO3 (65~68%) as starting materials. Lanthanum oxide is doped in barium titanate powders to prepare ceramics by pelleting, forming, dumping, sintering and other steps. The structure and morphology of ceramics are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric constant and dielectric loss are obtained by dielectric frequency analyzer. The results show that grain size and tetragonality of the barium titanate ceramics doped by lanthanum oxide sintered at 1270 °C for 3 h are found to decrease with the increase of dopants concentration. Dielectric constant increases at first and then decreases as La2O3 concentrations grow, reaching the maximum value when the concentration is 0.3 mol%. The ceramic samples transform from normal ferroelectric to the ferroelectric with diffused phase transition. [ABSTRACT FROM AUTHOR]