Coreeshell structured Bi_(0.5)Na_(0.5)TiO_(3)eKTaO_(3)þx%(in mass)Li_(2)CO_(3)ceramics were fabricated in this study.Increasing x from 0 to 2 leads to the decrease of sintering temperature from 1175℃to 1020℃.Th...Coreeshell structured Bi_(0.5)Na_(0.5)TiO_(3)eKTaO_(3)þx%(in mass)Li_(2)CO_(3)ceramics were fabricated in this study.Increasing x from 0 to 2 leads to the decrease of sintering temperature from 1175℃to 1020℃.The limited diffusion of Ta5þresults in chemical heterogeneities and coreeshell microstructures.The Ta5þ-depleted cores show the nanodomains(~10 nm),while the Ta^(5+)-rich shells display the polar nanoregions(1e2 nm).From x¼0 to 1,the appearance of cores with nanodomains contributes to the increase of dielectric constant and maximum polarization,while the further addition of Li2CO3 suppresses the dielectric and polarization responses due to the reduced grain sizes and polarization coupling.The enhanced dielectric relaxation and existence of core-shell microstructure with different polarization levels help to optimize the dielectric temperature stability.The x¼2 ceramics exhibit a stable high dielectric constant~1400 over a wide temperature range of 20e520℃.More encouragingly,the ultrafine grain size and coreeshell microstructure in the x¼2 ceramics greatly benefit the improvement of breakdown strength.Combined with the delayed polarization saturation and high ergodicity,a high recoverable energy density of~5.07 J/cm3 is obtained under 44 kV/mm,with a high efficiency of~85.17%.展开更多
The article describes the approaches for a reliable,quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds.The combination of scanning el...The article describes the approaches for a reliable,quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds.The combination of scanning electron microscopy(SEM)and transmission electron microcopy(TEM)with electron-probe analytical techniques,such as energy-dispersive X-ray spectroscopy(EDS),wavelength-dispersive X-ray spectroscopy(WDS)and electron-energy-loss spectroscopy(EELS)makes it possible to determine the true chemical composition,from precursor powders to synthesized ceramics or single crystals.The microscale(SEM)and nanoscale(TEM)analytical methods also give an insight into the local variations of the chemical composition.展开更多
基金supports from the National Key R&D Programof China(Grant No.2021YFB2012100)and the Special Funding Support for the Construction of Innovative Provinces in Hunan Province of China(Grant No.2020GK2062).Xuefan Zhou(Postdoc)is particularly grateful for the support from the China National Postdoctoral Program for Innovative Talents(Grant No.BX2021377).
文摘Coreeshell structured Bi_(0.5)Na_(0.5)TiO_(3)eKTaO_(3)þx%(in mass)Li_(2)CO_(3)ceramics were fabricated in this study.Increasing x from 0 to 2 leads to the decrease of sintering temperature from 1175℃to 1020℃.The limited diffusion of Ta5þresults in chemical heterogeneities and coreeshell microstructures.The Ta5þ-depleted cores show the nanodomains(~10 nm),while the Ta^(5+)-rich shells display the polar nanoregions(1e2 nm).From x¼0 to 1,the appearance of cores with nanodomains contributes to the increase of dielectric constant and maximum polarization,while the further addition of Li2CO3 suppresses the dielectric and polarization responses due to the reduced grain sizes and polarization coupling.The enhanced dielectric relaxation and existence of core-shell microstructure with different polarization levels help to optimize the dielectric temperature stability.The x¼2 ceramics exhibit a stable high dielectric constant~1400 over a wide temperature range of 20e520℃.More encouragingly,the ultrafine grain size and coreeshell microstructure in the x¼2 ceramics greatly benefit the improvement of breakdown strength.Combined with the delayed polarization saturation and high ergodicity,a high recoverable energy density of~5.07 J/cm3 is obtained under 44 kV/mm,with a high efficiency of~85.17%.
基金The authors wish to acknowledge the-nancial support of Slovenian Research Agency(P2-105)the Ministry of Higher Education,Science and Technology of Slovenia,the 5 FP project LEAF,the 6FP project IMMEDIATE and the 6FP NoE MIND.
文摘The article describes the approaches for a reliable,quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds.The combination of scanning electron microscopy(SEM)and transmission electron microcopy(TEM)with electron-probe analytical techniques,such as energy-dispersive X-ray spectroscopy(EDS),wavelength-dispersive X-ray spectroscopy(WDS)and electron-energy-loss spectroscopy(EELS)makes it possible to determine the true chemical composition,from precursor powders to synthesized ceramics or single crystals.The microscale(SEM)and nanoscale(TEM)analytical methods also give an insight into the local variations of the chemical composition.
