Microstructure and Dielectric Properties of Lanthanum Doped Barium Titanate

Abstract

Barium titanate has a special place in the group of ferroelectric perovskites because it can be formulated in a large number of systems and solid solutions that provide a wide range of various applications. The perovskite structure has capability to host ions of different size, so a large number of different dopants can be accommodated in the BaTiO3 lattice [1]. It was detected that various substitutions of Ba2+ and Ti4+ ions can affect on changing of microstructure and electrical properties of barium titanate ceramics.

In this work, a polymeric precursors method was used to prepare pure and barium titanate doped with different concentration (0.3 and 0.5 mol %) of lanthanum. Obtained powders were nanosized but they were also highly agglomerated. However, obtained powders were pressed in to pellets and sintered at 1300 oC for 8h in air atmosphere. Previously analyzed microstructures reveal that the relatively short time of sintering (2h) was not enough for significant grain growth [2].

The formation of phase and crystal structure of BaTiO3 was carried out by XRD analysis. Microstructural properties such as grain size distribution and morphology of sintered samples were determined using scanning electron microscope (fig.1.). Average grain size from 0.75-1.0 μm was found in samples with 0.3 mol% La while samples with 0.5 mol % La show average grain size from 0.2-0.4 μm. Therefore, it was detected the influence of lanthanum concentration on grain growth. Electrical measurement of BT ceramics were carried out and it was observed lanthanum influence on shifting of BT Curie temperature from TC = 119 oC for pure to 115 and 89 oC for samples doped with 0.3 and 0.5 mol% of La [3]. It was also detected the effect of lanthanum concentration on increasing of dielectric constant (fig.2)