Effects of nickel addition on the microstructure and dielectric property of barium titanate powder and ceramic with excessive Ti

The nanocrystalline powders and ceramics of nickel-doped BaTiO_3 with Ti/Ba=1.02 were prepared by Sol-Gel process.The powders and ceramics were characterized by XRD,SEM and TEM methods.And the dielectric properties of the ceramics were determined.The results showed that the powders with particles around 40 nm are mainly composed of cubic BaTiO_3 and a little BaCO_3.After sintering the cubic BaTiO_3 and BaCO_3 can be transformed into tetrahedron BaTiO_3 phase.The sintering temperature can be decreased ~100 ℃ because of the doping of nickel.When Ti/Ba=1.02,with the increase of nickel content,the grain size of the ceramics increased firstly and then decreased.And as the nickel mol ratio is 3.0%,the e_m of the fine-grained ceramics have high e_m(5 571) and low tanδ(0.011).Compared with the ceramics with Ti/Ba=1.00,the peak of e-T curve of the nickel-doped BaTiO_3 with excessive Ti decreased because of its fine grain.