| Barium titanate based ceramic capacitors are multi-functional material, it belongs to low frequency and high dielectric ceramic capacitor, that is II type strong dielectric ceramics. Traditional lead dielectric ceramic materials are harmful to the environment and human health, especially with the European Union make the implementation of lead-free, Therefore, to find a new, environmental friendly, high-performance lead-free ceramic capacitor is important. To find one or several ceramic systems through doping rare-earth have become the common goal to satisfy people's needs; according to the standard of U.S. Electronics Industry Association (EIA), the operating temperature of Y5P is narrow relatively compared to the X7R, X8R, Y5V, but higher temperature is stable, it can be applied in the higher temperature-stable ceramic capacitors.In this paper, the BaTiO3-Nb2O5-Fe2O3 systems was researched. respectively, the dielectric properties and crystal structure of system with different Nb2O5 and Fe2O3 was studied. It is showed that Y5P ceramic capacitors can be obtained when doping 1.00wt% and 0.1 wt% Nb2O5 and Fe2O3, and its structure is mainly paraelectric phase and ferroelectric phase. To improve the temperature stability and to ensure a high dielectric constant, functional ceramics were prepared using a variety of rare earth (La2O3, CeO2, Bi4Ti3O12) doping barium titanate ceramics, At the same time, the microstructure and electrical properties of the system was investigated using XRD, SEM and other testing methods. The system can be used in the future by doping different rare earth and changing processes of samples to achieve practical applications.All micro-structure of samples were investigaed by XRD. The results showed that A or B site substitution occurred by doping rare earth with appropriate amount, making rare earth ion solute in the crystal lattice, the structure of all samples are perovskite. All ceramic and film morphology of the samples were studed by comparativing SEM graph. The results showed that all the doped-rare earth ceramics exists grain. But excessive sintering additives (glass powders), the microstructure of ceramic samples is not to distinguish between grain and grain boundary. The type and composition of rare earth influence on the grain size and shape, a large number of La2O3 inhibit the grain growth, there is also some samples of abnormal grain growth, the grain size and shape were impacted by the type and proportion of rare earth, warming rate, holding time and oxygen partial pressure.In the system, doping BIT and CeO2 to overcome the Curie temperature sudden jump and low dielectric constant at room temperature. Ce4+ into the B site, part of the cell showed a symmetry center, making BaTiO3 ceramics polarization irregular, to impove Tc and dielectric properties. Due to the high sintering temperature, the doping glass powders into BaTiO3 was uesed. It can be promoted mass trasfer and decreased sintering temperature, the condense of samples improved. In this study, Y5P ceramics with high stability and high dielectric can be prepared successfully. At 1kHz, the performance parameters is 1300℃sintered,ε≈4000, tanδ≤1.5%, at -30℃-85℃,-10%<Δε/ε<10%.Different rare earth doped barium titanate to influenced Y5P ceramics was analyzed. And optimum calcination temperature was determined by comparing different calcination temperature. Finally, the BaTiO3-Nb2O5-Fe2O3 system, was prepared successfully through doping rare-earth and choosing appropriate sintering temperature, holding time to obtained Y5P ceramic capacitors with high stability, high-dielectic. |
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