The CaF_(2)-4LiF additive was added into SrTiO_(3)ceramics in order to decrease the sintering temperature for compact pulse power application.The crystalline structure,microstructure and energy storage performance of sintered ceramics were studied.Incorporating CaF_(2)-4LiF additive to SrTiO_(3)ceramics contributes to a notably enhancement of the energy storage density.The great enhancement in energy storage density occurred due to the notable increase in breakdown strength and the refinement of microstructure.With 2 at%additive,the samples exhibited an average breakdown strength of 31.8kV/mm,and an energy storage density of 1.212 J/cm^(3)which is about 1.4 times higher than pure SrTiO_(3).
A density functional plane-wave pseudopotential method is used to study the doping mechanisms of impurity defects（BiBa, YTi） in BaTiO3- BiYO3. Single BiBa and YTi impurities have little structure distortion. Bi forms ionic bond with nearby O atom in single Bi impurity, Y formed [YO6] octahedral in single Y impurity. However, in the co-doped BiB~ and Yr~ structure, Bi formed three valence bonds with nearby O atom, which causes the large structure distortion. The doped ion makes the mobile of Ti4~ difficult and loss local ferroelectricity, which will broaden the dielectric constant temperature curve and increase the temperature stability of BaTiO3 ceramic matrix.
In the current work,the bulk ternary(0.85-x)BiFeO3-xBaTiO3-0.15PbTiO3(BF-BTx-PT,x=0.08-0.35)system has been studied as a potential high-temperature piezoceramics.Samples with various content of BT were prepared via solid-state route,and pure perovskite phase was confirmed by X-ray diffraction.The temperature dependence of dielectric constants confirmed the decrease of Curie temperature with increasing BT content.It was found that the morphotropic phase boundary(MPB)composition of BF-BTx-PT ceramics was in the vicinity of x=0.15,which exhibits optimal properties with piezoelectric constant d33 of 60 pC/N,high Curie temperature of 550℃,and low sintering temperature of 920℃.Measurements also showed that the depoling temperature was 300℃,about 150℃higher than that of commercialized PZT ceramics,which indicated good temperature stability.BF-BTx-PT ceramics are promising candidates for high temperature applications.
Zhonghua YAOYing LIUZhe SONGZhijian WANGHua HAOMinghe CAOZhiyong YUHanxing LIU
