A solid state reaction method was used to synthesize barium titanate （BT） and barium cerium titanate （BCT） ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium （Ce） on the structure, microst...A solid state reaction method was used to synthesize barium titanate （BT） and barium cerium titanate （BCT） ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium （Ce） on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy （SEM） investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction （XI^D） patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current （dc） density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.展开更多
The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has ...The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has been recognized as a viable strategy to foster the stability of RuO_(2)for acidic OER applications.This study presented an ion that does not readily gain or lose electrons,Ba^(2+),into RuO_(2)(Ba-RuO_(2))nanosheet(NS)catalyst that increased the number of exposed active sites,achieving a current density of 10 mA/cm^(2)with an overpotential of only 229 mV and sustaining this output for over 250 h.According to density functional theory(DFT)and X-ray absorption spectroscopy,Ba doping resulted in a longer Ru-O bond length,which in turn diminished the covalency of the bond.This alteration curtailed the involvement of LO and the dissolution of ruthenium(Ru),thereby markedly improving the durability of the catalyst over extended periods.Additionally,attenuated total reflectance-surface enhanced infrared absorption spectroscopy analysis substantiated that the OER mechanism shifted from a LO-mediated pathway to an adsorbate evolution pathway due to Ba doping,thereby circumventing Ru over-oxidation and further enhancing the stability of RuO_(2).Furthermore,DFT findings uncovered that Ba doping optimizes the adsorption energy of intermediates,thus enhancing the OER activity in acidic environments.This study offers a potent strategy to guide future developments on Ru-based oxide catalysts'stability in an acidic environment.展开更多
Glass ceramics Ba2LaFT：xDy3＋ are obtained through the conventional melt-quenching technique, and their lu- minescent properties are investigated. Under 350 nm excitation, the emission spectra consists of a strong bl...Glass ceramics Ba2LaFT：xDy3＋ are obtained through the conventional melt-quenching technique, and their lu- minescent properties are investigated. Under 350 nm excitation, the emission spectra consists of a strong blue- yellow band as well as a weak red emission centered at 660 nm, which are attributed to the 4F9/2 →6H15/2, 4F9/2→6H13/2 and 4F9/2 → 6Hll/2 transitions of the Dy3＋ ion, respectively. The corresponding Commission Internationale de L＇Eclairage （CIE） chromaticity coordinate for a sample of 2 mol.% Dy203 after being heat-treated at 690℃ is （0.313, 0.328）. It is concluded that the formed materials may have the possibility of applications for white light-emitting diodes （LEDs）.展开更多
文摘A solid state reaction method was used to synthesize barium titanate （BT） and barium cerium titanate （BCT） ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium （Ce） on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy （SEM） investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction （XI^D） patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current （dc） density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.
基金supported by Young Project of Education Department in Guizhou Province(No.2022099)the Natural Science Special of Guizhou University(No.X202220 Special Post A)the National Natural Science Foundation of China(Grant No.22208071)。
文摘The persistent stability of ruthenium dioxide(RuO_(2))in acidic oxygen evolution reactions(OER)is compromised by the involvement of lattice oxygen(LO)and metal dissolution during the OER process.Heteroatom doping has been recognized as a viable strategy to foster the stability of RuO_(2)for acidic OER applications.This study presented an ion that does not readily gain or lose electrons,Ba^(2+),into RuO_(2)(Ba-RuO_(2))nanosheet(NS)catalyst that increased the number of exposed active sites,achieving a current density of 10 mA/cm^(2)with an overpotential of only 229 mV and sustaining this output for over 250 h.According to density functional theory(DFT)and X-ray absorption spectroscopy,Ba doping resulted in a longer Ru-O bond length,which in turn diminished the covalency of the bond.This alteration curtailed the involvement of LO and the dissolution of ruthenium(Ru),thereby markedly improving the durability of the catalyst over extended periods.Additionally,attenuated total reflectance-surface enhanced infrared absorption spectroscopy analysis substantiated that the OER mechanism shifted from a LO-mediated pathway to an adsorbate evolution pathway due to Ba doping,thereby circumventing Ru over-oxidation and further enhancing the stability of RuO_(2).Furthermore,DFT findings uncovered that Ba doping optimizes the adsorption energy of intermediates,thus enhancing the OER activity in acidic environments.This study offers a potent strategy to guide future developments on Ru-based oxide catalysts'stability in an acidic environment.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275180 and51472125)the K.C.Wong Magna Fund of Ningbo University
文摘Glass ceramics Ba2LaFT：xDy3＋ are obtained through the conventional melt-quenching technique, and their lu- minescent properties are investigated. Under 350 nm excitation, the emission spectra consists of a strong blue- yellow band as well as a weak red emission centered at 660 nm, which are attributed to the 4F9/2 →6H15/2, 4F9/2→6H13/2 and 4F9/2 → 6Hll/2 transitions of the Dy3＋ ion, respectively. The corresponding Commission Internationale de L＇Eclairage （CIE） chromaticity coordinate for a sample of 2 mol.% Dy203 after being heat-treated at 690℃ is （0.313, 0.328）. It is concluded that the formed materials may have the possibility of applications for white light-emitting diodes （LEDs）.
