SYNTHESIS AND CHARACTERIZATION OF BaTiO3-BASED CERAMICS DOPED IN B SITE BY BaTi_(1-x)Nb_xO3

摘要

In this work, the substitution of Nb~(5+) ions into the B site of BaTiO3 ceramics by mechanism BaTii-xNbxOa (x= 0.001,0.003,0.005, 0.04, 0.08,0.20, and 0.25) have been investigated regarding their microstructural and dielectric properties. The ceramics powders were successfully prepared by a conventional solid-state synmesis in air atmosphere. The main objective was to study the effect of the addition of Nb~(5+) on the structure and electrical properties of barium titanate. The phases formed, the crystal structure and the microstructure of the samples were characterized using X-ray diffraction (XRD), raman spectroscopy and scanning electron microscopy (SEM). The modified BaTiO3 dielectric ceramics prepared by conventional solid-state route in air atmosphere exhibit single perovskite structure and improved electrical properties; the results shows that the addition of a small amount of Nb~(5+) gradually changes me crystal structure from a typical tetragonal-pseudocubic structure. The results of permittivity measurements shows the difficulty in obtaining, electrically homogeneous samples by solid-state method. A secondary phase (BasTi3Nb4O_(24)) start to appear as the doping content of Nb~(5+) ≥ 0.25, indicating that the solubility limit of Nb~(5+ )in BaTiO3 reached. Pellets derived of me samples with x= 0.005 and sintered at 1500 °C exhibit optimum properties of dielectric constant decreasing to 90°C curie point. The effects of dielectric and ferroelectric properties of samples are also investigated.