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Preparation and Research of Y5V-type Barium Titanate-based Nanopowders and Dielectric Ceramics by Sol-gel Method

Author: XingDaiLin
Tutor: GuoHuiLin；CuiBin
School: Northwestern University
Course: Materials Physics and Chemistry
Keywords: Barium titanate Sol-gel method Doping Dielectric properties Y5V
CLC: TQ174.1
Type: Master's thesis
Year: 2010
Downloads: 105
Quote: 1
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Abstract


Barium titante is an important high-quality electronic materials and being widely used in many areas. Barium titante-based multilayer ceramics capacitors (MLCC) with a small bulk, large specific votume, high reliablity, can meet the current demand of the miniaturization and integreated of the electronic circuits. The Y5V-type MLCC has a large dielectric constant and high temperature stability, thus has a large market. The morphology and properties of barium titanate nano-powders are closely related to the preparation technology, so the preparation methods and doping styles have been a hot reaearch domain. The BaTiO3-based powders prepared via sol-gel methed have the merites of high purity, uniformity, small size, so it is used widely.Barium titanate doped with a various elements was prepared by sol-gel process. The kind of the doping element, effect of doped concentration and technical parameter on the phase, morphology and dielectric properties of powders and ceramics were investigated in this paper, in order to get the highly properties ceramics meeting the EIA Y5V stadard.The main research content are as follows:1. In order to study the influence of various factors on the dielectric properties of the ceramics, we designed a 5 level 4 factors [L16(45)] orthogonal table, and prepared the BSCTZS-based nano-powders and ceramics by sol-gel method. The results showed that the factors affect the dielectric constant is Ti/Ba>Zr>Nb>Ce>Zn in turn. And we can predict the best formula for the dielectric constant is A3B1C2D2E2.2. Ce-modified (Ba0.87Sr0.04Ca0.09)(Ti0.90Zr0.04Sn0.06)O3 (BSCTZS) powders and ceramics were prepared by using the sol-gel process. The influence of the concentration of Ce on the microstructure and dielectric properties of powders and ceramics had been investigated. The results indicated that the powders synthesized by sol-gel process calcined at 900℃for 2 h achieved nanometer size, with the grains mainly composed of the cubic BaTiO3 phase. With the increase of the Ce concentration, the grain size of the BSCTZS ceramics decreased. After sintering, the ceramics were completely consisted of the cubic BaTiO3 phase. The average grain size and the relative density decreased as the Ce concentration increased. Moreover, the maximum dielectric constant (εmax) decreased and the Cuire temperature (Tm) shifted to lower temperature at the same time. Furthermore, it is shown that the BSCTZS ceramics have a relatively high dielectric constant in a wide temperature rage. When Ce concentration was 0.15mol%, BSCTZS 15 ceramics meeting the EIA "Y5V" specifications and theεr(25℃) is higher than 7500.3. (Ba0.87Sr0.04Ca0.09)(Ti0.96-xZrxSn0.06)03 (BSCTZS) powders and ceramics were prepared by using the sol-gel process. The influence of the concentration of Zr on the microstructure and dielectric properties of powders and ceramics had been investigated. The results indicated that the as-synthesized powders had a nanometer-scale grain size, with the grains mainly composed of the cubic BaTiO3 phase. After sintering, the ceramics consisted entirely of the cubic BaTiO3 phase. Moreover, the maximum dielectric constant (εmax) first increased and then decreased and the Curie temperature (Tm) shifted to a lower temperature with a broaden Curie peak. Furthermore, When the Zr concentration was 8.0 mol%, the dielectric properties of BSCTZS ceramics met the Electronic Industries Alliance (EIA) Y5V specifications and theεr(25℃) was higher than 13200.4. Nb-doped (Ba0.87Sr0.04Ca0.09)(Ti0.86Zr0.08Sn0.06)03 (BSCTZS) powders and ceramics were prepared by using the sol-gel process. The influence of the concentration of Nb on the microstructure and dielectric properties of powders and ceramics had been investigated. The maximum dielectric constant (εmax) first increased and then decreased and the Curie temperature (Tm) shifted to a lower temperature with the increasing Nb content. Furthermore, When the Nb concentration was 0.38 mol%, the BSCTZS ceramics met the Electronic Industries Alliance (EIA) Y5V specifications and theεr(25℃) was higher than 16200.

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