Papers by Keyword: Barium Titanate Ceramics

Abstract: GeO₂ has been doped solely and together with SiO₂ into barium titanate ceramics by mixing and calcination. The microstructure and dielectric properties of doped BaTiO₃ have been characterized. When doped in BaTiO₃, Ge⁴⁺ ion could incorporated into the crystal lattice of BaTiO₃ to occupied Ti⁴⁺ sites. For relative smaller Ge⁴⁺ ion, the tetragonal phase could be enhanced. As dielectric properties have strong relation to tetragonal phase. The relative permittivity could be increased in this mechanism. However, the high leakage current which induced by more ionic defect was also lead to high dielectric loss. Besides, the assemble in grain boundary by Ge⁴⁺ ion may also have effect. Results on the GeO₂-SiO₂ co-doped sample showed that the mechanisms of Ge doping and Si doing could happen at one time.

Abstract: Barium titanate (BaTiO3) ceramics with grain size varied from 1000 to 8 nm were prepared by two step sintering method (TSS) and spark plasma sintering (SPS), respectively. Mixture structures of BaTiO3 ceramics were proved by in-situ temperature high resolution x-ray diffraction. Multiple ferroelectric domains present in nano-crystalline BaTiO3 ceramics were observed by transmission electron microscope. The evolution of phase transitions supported the existence of intrinsic mechanism. Dielectric loss of fine grain size BaTiO3 was higher than coarse grain size during Curie phase transition due to diffuse phase transition and grain boundary effects.

Abstract: CuO has been doped solely and together with BaO and SiO₂ into barium titanate by mixing and calcination. X-ray diffraction showed that the sample doped by CuO-BaO has stable second hexagonal phase while the samples doped by CuO, CuO-SiO₂ were of a pure perovskite phase. For CuO-BaO doping, the Curie temperature was decreased accompanied with higher εmax; while for CuO doping and CuO-SiO₂ codoping, the Curie temperature was increased with εmax decreased. The difference can be explained considering that Cu²⁺ ion could not only incorporate into the BaTiO₃ lattice, but also assemble in the boundary phase when CuO was doped solely. Besides, the mechanisms of CuO doping and SiO₂ doping could happen at one time.