Structure And Properties Of Barium Strontium Titanate-based Relaxor Ferroelectric Ceramics For Energy Storage

With the development of electronic industry, dielectric materials that can provide high power density and energy density, is in urgent needed. These kind of materials are wildly used in grid system, pulse power, hybrid car and other fields.(Ba,Sr)Ti O3 ceramics were chosen as the research objective in this article, the influence of Ba/Sr ratio, substitution with Bi3+, CaZrO3 doping and the process on crystal structure, micro-structure, dielectric properties, breakdown strength and energy storage characteristic of(Ba,Sr)TiO3 based ceramics were studied.(BaxSr1-x)0.85Bi0.1TiO3 ceramics were prepared via the solid reaction process. The energy storage properties were studied. It`s found that as the concentration of barium increased the dielectric constant increased and the breakdown strength decreased at room temperature. The Curie temperature moved to room temperature, P-E curve showed ferroelectric hysteresis loop. When x was below 0.8, the dielectric loss keeps in a quite low order of magnitude. When x was up to 0.8, the dielectric loss increased to about 10-3, and the energy storage efficiency was decreased to 69.35%. The temperature stability was also damaged. Take various factors into accont,(Ba0.6Sr0.4)1-3/2xBixTiO3 ceramics were chosen for further study.The structure and dielectric properties of(Ba0.6Sr0.4)1-3/2xBixTiO3 ceramics(0.4? x? 1.0) were studied. XRD results indicated the formation of solid solution for x?1.0. It was found Bi3+ substituted in the perovskite structure could promote sintering and lower sintering temperature. With the concentration of bismuth increased, the curie peak was compressed and broadened, the Curie temperature moved toward low temperature. Meanwhile, the ceramics showed typical relaxor characteristics and the relaxation factor increased with Bi substitution. Accordingly, the energy storage efficiency increased from 60.80%(x=0.4) to 75.74%(x=1.0) at E=70kV/cm. The breakdown strength increased, dielectric constant and dielectric loss at room temperature decreased with the Bi content.The influences of Ca ZrO3 dopants on the structure, dielectric properties, breakdown strength and energy storage characteristics were studied. It was founded that the doping of CaZr O3 into(Ba0.6Sr0.4)1-3/2xBixTiO3 ceramics improved the breakdown strength significantly. When the concentration of CaZrO3 reached 7.5wt%, the breakdown strength was as high as 19.9kV/mm, and then decreased slightly with more CaZrO3 dopant. At the same time, CaZr O3 could improve the relaxation behavior. When the concentration of Ca Zr O3 was 5.0wt%, the relaxation factor reached 1.78, and the energy storage efficiency reached the maximum.To meet the demand of large size ceramics in practical work, cold isostatic pressing was used to prepare large size specimens. A large dark area was observed in the large-size sample sintered in air, and the breakdown strength deteriorated. To solve this problem, the influence of sintering atmosphere was studied. It indicated that the dark hole could eliminate in the large-size sample sintered in oxygen, and the breakdown strength improved accordingly.