Papers by Keyword: Dielectric Breakdown Strength

Abstract: Sr_0.7Bi_0.2TiO₃ (SBT), a kind of lead-free relaxor ferroelectric, is attracting more and more attention for pulse energy storage applications due to the low remnant polarization and high energy storage efficiency (h). However, relatively low dielectric breakdown strength (DBS) limited the recoverable energy storage density (W_rec). Herein, CaTiO₃ with high intrinsic DBS was introduced in SBT. The novel solid solutions (1-x)SBT-xCT with x = 0 - 0.15 shows pure pseudo-cubic perovskite structure. When x = 0.05, the maxium polarization are improved, and the CT doping decreases the average grain size, leading to an enhanced DBS. A high energy storage properties of 1.59 J/cm³ with the h of 87.4% at 220 kV/cm is achieved in 0.95SBT-0.05CT, which demonstrates that this 0.95SBT-0.05CT is prospective materials for energy storage application.

Abstract: In this work, a series of (1-x)Sr_0.7Ba_0.3Nb₂O₆-xSr_0.7Bi_0.2TiO₃ ceramics were formulated by a phase-mixed sintering, the microstructure and energy storage performance were studied. The introduction of SBT induces the formation of equiaxed crystals leading to the denser microstructure, thus improving the dielectric breakdown strength. In addition, the enhancement of relaxor behavior improves the energy storage performance. For 0.94Sr_0.7Ba_0.3Nb₂O₆-0.06Sr_0.7Bi_0.2TiO₃, an energy storage density of 0.49J/cm³ and an efficiency of 94.2% were achieved.

Abstract: Al₂O₃ ceramics with CaO-SiO₂-MgO (CMS), Yb₂O₃ and ZrO₂ additives were fabricated by a conventional solid-state reaction method. The effects of ZrO₂ dopant on phase compositions, microwave dielectric properties and dielectric breakdown strength of Al₂O₃ ceramics were studied. XRD demonstrated that CaAl₂Si₂O₈ and Zr &Y compound phases co-existed with alumina. SEM exhibited that ZrO₂ dopant could refine the grain of alumina ceramics and improve its relative density. With ZrO₂ content increasing from 1wt% to 5wt% ε_r increased from 9.8 to 10.25, but Q×f decreased from 52823GHz to 35922GHz. The breakdown strength increased initially and reached the maximum value at ZrO₂=3wt%. When ZrO₂ content is 3wt%, the comprehensive performances were the best: E_b= 37.37kV/mm for 1mm samples and 17.26kV/mm for 3mm samples, Q×f = 37044 GHz, ε_{r =} 10.01, and τ_{f =} -52 ppm/°C.

Abstract: The dielectric breakdown strengths of two series of sintered alumina samples of low and high impurity content (where Si is the dominant element with, respectively, 90 and 1500 ppm) and impurity level (25 ppm of Si and 12 ppm of Ti) are compared with positron lifetime measurements. The dielectric breakdown strength of sintered alumina is found higher than that of single crystal. This improvement is stronger when silicon is the only major foreign element. If, in addition to SiO2, MgO and CaO are present in substantial amounts, the improvement is lessened. This is attributed to the enhanced bulk solubility of Si. These results are discussed by calling for the potential traps for positrons and electrons that are located at grain boundaries. It is deduced that the improvement of the dielectric breakdown strength stems from the consequences of Si segregation at grain boundaries via electron trapping in shallow traps, which are likely the x '' Al • Al ) V : (3Si clusters.