Dielectric Properties Of Rare-earth Doped Barium Titanate Ceramics Derived From Sol-hydrothermally Synthesized Nanopowders

With the miniaturization and high-capacity demand for the ceramic capacitors, it is urgent to seek dielectric materials with high-performcance. Monodisperse Rare-earth(Dy³⁺, Nd³⁺, Y³⁺) doped barium titanate nanopowders with spherical morphology has been synthesized via a modified sol-hydrothermal method. Thereafter, the ceramics has been prepared by a convertional pressureless sintering technology, and the dielectric properties of sintered ceramics have been studied. It is found that the grian growth is supressed due to the incoporation of the rare-earth ions.The possible occupation of the Dy³⁺ has been preliminary extrapolated based on the variation of lattice volume and phase composition. A self-compensation mode involving the simultaneously occupation at Ba-site and Ti-site is observed in the samples with 4 mol% Dy. Importantly, stabilized temperature-dependent dielectric properties has been achieved, resulting from the diffuse phase transition behaviors induced by chemical inhomogeneity.The bond bingding energy, element chemical enviroment and order-disorder structure of BT has been characterized by X-ray photoelectron diffraction, electron paramagentic resonance and photoluminescence. It is demonstrated that Nd³⁺ tends to enter into the Ba-site, inducing the formation of Ba vacancies and O vancacies to compensate the valance balance. Further, according to the temperature-dependent X-ray diffraction analysis, it is confirmed that typical orthorombic-tetragonal phase transition exsits in pure BT near the room temperature. While in the samples with 0.5 mol% Nd, the colossal permittivity?⁷50000? near the room temperature is caused by the phase coexist between an unknown and tetragonal structure.Through the comparsion of the influence of Y and Nd/Y on BT, it is concluded that Y³⁺ prefers to substitute the Ti4+ site in both solo-doped and co-doped samples. The incoporation of Y³⁺ has no effect on the shift of the Curie temperature in the Y-doped BT ceramics. However, the Curie peaks decreased with a wide distribution due to the co-incorporation of the Nd and Y ions. In this situation, Nd³⁺ makes great contribution to the decrease of the Curie temperature and the introduction of Y³⁺ is the main factor causing the wideness of the dielectric peaks.