Preparation And Dielectric Properties Of Doped Barium Titanate Powders And Ceramics

Barium titanate has high dielectric constant and was used widely in multiplayer ceramic capacitors (MLCCs) as dielectrics. The reaserch of preparation and dielectric properties of doped barium titanate has been a focal point in the field of electronic ceramics. Nb2O5-Co2O3-Re2O3 doped barium titanate has high dielectric constant and modified temperature behaviors. The preparation and doping method influences the electrical properties of barium titanate strongly. Sol-gel method can prepare multicomposition barium titanate powders. So in this paper Nb2O5, Co2O3, NiO, Nd2O3 and Nb2O5-Co2O3- Nd2O3 doped barium titanate powders and ceramics were prepared by sol-gel method. The powders and ceramics were characterized by XRD, SEM and TEM methods. The dielectric properties of the ceramics were determined.In general, the main work is as follows:1. Preparation and dielectric properties of barium titanateThe nanocrystalline barium titanate powders were prepared by sol-gel method calcined at 800C for 2h. The influence of calcined temperature, Ti/Ba ratio, fired temperature on the microstructure and dielectric properties were investigated. The results showed that: with the increasing of calcined temperature, the grains grows obviously and the ceramics become more density. The optimal fired temperature was 1300C.2. Preparation and dielectric properties of Nb-doped barium titanateFirstly, H3[Nb(O2)4] solution was synthesized, its concentration was determined. Then the Nb-doped barium titanate powders were prepared by sol-gel method. With the increasing of Nb, the grain size of ceramics decreased greatly and the fired temperature were lowered. The Tc shifted to lower temperature and the max decreased while the amount of Nb were increased.3. Preparation and dielectric properties of Nd-doped barium titanate Nd-doped barium titanate powders and ceramics were prepared by sol-gelmethod. With the increasing of Nd, the Tc was lowered and the dielectric constant decreased. The ceramics has little pores and high density when the Ti/Ba was high.The variation of Ti/Ba ratio has little effect on the Tc, while the max increased firstly and then decreased with the increasing of Ti/Ba ratio. The ceramics of Ti/Ba=1 .02 has good dielectric properties.4. Preparation and dielectric properties of Co,Ni doped barium titanateCo2O3 and NiO can decrease the fire temperature of BaTiO3 based ceramics. When the two oxides were doped, the Tc shifted to lower temperature. The dielectric constant of Co-doped barium titanate ceramics was higher than that doped with Ni.5. Preparation and dielectric properties of Nb-Co-Nd doped barium titanate Nb-Co-Nd doped barium titanate powders and ceramics were prepared by sol-gelmethod. The influence of calcined temperature, Nb/Co ratio, doping method on the microstructrue and dielectric properties were investigated. The results showed that: the ceramics calcined at 1150C/2h has core-shell structure by solid doping. When the additives were doping by liquid, the ceramics calcined at 1200C/2h has similar structure which has high dielectric constant at room temperature(3550) and good temperature behavior.In general, Nb, Co, Nd doped barium titanate powders and ceramics were prepared respectively by sol-gel method in this paper. The influence of doping amount, calcined temperature, Ti/Ba ratio to the microstructure and dielectric properties were investigated. Upon this basis, Nb-Co-Nd doped barium titanate powders and ceramics were prepared by sol-gel method which has good dielectric properties when calcined at 1200C for 2h.