Hybrid electric cars and pulsed power technologies have increased the demand for capacitors with high energy density, wide temperature stability, high operating voltage, and good mechanical qualities. In this work, (1 − x) (0.6Bi 0.5 K 0.5 TiO 3 -0.4BiFeO 3 )-x(Na 0.4 Sm 0.2 NbO 3 ) ((1 − x) (BKTBF)-xNSN) relaxor ceramics were prepared by constructing morphotropic phase boundary (MPB) combined with oxygen vacancy defect engineering. It is worth noting that the 0.6BKT-0.4BFO ceramics at MPB have a high P max ∼ 60 μC/cm 2 . The ultra-hard (H V = 10.7 GPa) BKTBFO-0.16NSN relaxor ferroelectric ceramic achieves a high W rec of 6.52 J/cm 3 , a working temperature of 20−120 °C, and a working frequency of 1−1000 Hz. Additionally, the BKTBFO-0.16NSN ceramic demonstrates comprehensive pulse charge−discharge performance (I max = 17.2 A, C D = 546.7 A/cm 2 , P D = 54.7 MW/cm 3 , and t 0.9 = 59 ns) and excellent stability (25−125 °C and 10 4 charge−discharge cycles). This study offers a novel approach for the practical implementation of high-performance pulse capacitors, which will undoubtedly stimulate further research and development of high-P max energy storage dielectrics (such as BNT, BKT, and BFO).
The K glasses with different Al 2 O 3 content were prepared. Different proportions (50, 55, 60, 65, 70 %) of the three glasses were respectively mixed with alumina ceramic-filler, then the mechanical and dielectric properties were investigated. The results showed K 2 O-B 2 O 3 -SiO 2 -2 %Al 2 O 3 glass/alumina filler (glass:alumina = 60:40) had the excellent comprehensive properties, so further study was continued with part of alumina ceramic-filler replaced by the silica ceramicfiller on this composite. Then the X-ray diffraction analysis revealed that the alumina and silica fillers existed as the crystal phase, and the densification was seriously damaged when the silica content reached to three quarters of the fillers. With the increase of the silica-filler, the composites' density and dielectric constant exhibited uniform decrease, but thermal expansion coefficient (TEC) uniformly increased. When the glass:alumina:silica was equal to 60:30:10, a best composite property was presented as a bulk density of 2.582 (g cm -1 ), a dielectric constant of 6.1 and a dielectric loss of 2 9 10 -3 at 1 MHz, a flexural strength of 168 MPa, and a TEC of 8.62 9 10 -6°C-1 .
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