MnO_2doped PbTiO_3 ceramics was prepared by means of solgel method, its density and some electric properties were investigated. The results showed that it was feasible to prepare multicomponent PbTiO_3 solgel series ...MnO_2doped PbTiO_3 ceramics was prepared by means of solgel method, its density and some electric properties were investigated. The results showed that it was feasible to prepare multicomponent PbTiO_3 solgel series with the aid of solgel method, the obtained MnO_2doped PbTiO_3 ceramics showed a highpurity, uniform component, better dense structure, hardly crack, and had good dielectric, piezoelectric, ferroelectric and pyroelectric properties.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
This paper presents a theoretical model for describing the thermodynamic properties of doped ferroelectric crystals based on a modifed Weiss mean-field approach.Accounting for quadrupole and octupole terms in the expr...This paper presents a theoretical model for describing the thermodynamic properties of doped ferroelectric crystals based on a modifed Weiss mean-field approach.Accounting for quadrupole and octupole terms in the expression for the effective field within the Weiss model makes it possible to move from the Langevin equation to the Landau--Ginzburg equation.Furthermore,the cofficients of the Landau-Ginzburg equation can be expressed in terms of the physical parameters of the crystal lattice.For these parameters,analytical ex pressions are proposed that describe their change when adding dopants in ceramic matrix composites.Perovskite barium titanate ceramics with a variety of inclusions is considered as an application example of the developed method.The obtained agreement between the analytical and experimental results for barium titanate ceramics with lanthanum/magnesium/zirconium dopants gives us hope of the applicability of the present theory to the calculation of other doped ferroelectrics as well.展开更多
CaCu（3-x）FexTi4O（12）（x=0, 0.015, 0.03, 0.045, 0.06） ceramics were synthesized by sol-gel method. The electrical conduction and dielectric measurements show that the doping of a very small amount of Fe（3＋） ion...CaCu（3-x）FexTi4O（12）（x=0, 0.015, 0.03, 0.045, 0.06） ceramics were synthesized by sol-gel method. The electrical conduction and dielectric measurements show that the doping of a very small amount of Fe（3＋） ions greatly reduces the low-frequency dielectric constants and leakage, and enhances grain resistivity. For the doped samples, the appearance of the strong low-frequency peaks in the spectra of dielectric loss confirms that the doping of Fe（3＋） ions induces the contact-electrode effect on ceramic surface. These great changes of electrical properties may originate from the reduced amount of oxygen vacancies by doping Fe（3＋）展开更多
文摘MnO_2doped PbTiO_3 ceramics was prepared by means of solgel method, its density and some electric properties were investigated. The results showed that it was feasible to prepare multicomponent PbTiO_3 solgel series with the aid of solgel method, the obtained MnO_2doped PbTiO_3 ceramics showed a highpurity, uniform component, better dense structure, hardly crack, and had good dielectric, piezoelectric, ferroelectric and pyroelectric properties.
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）.
基金This work is supported by the Russian Science Foundation under grant No.19-79-10074.
文摘This paper presents a theoretical model for describing the thermodynamic properties of doped ferroelectric crystals based on a modifed Weiss mean-field approach.Accounting for quadrupole and octupole terms in the expression for the effective field within the Weiss model makes it possible to move from the Langevin equation to the Landau--Ginzburg equation.Furthermore,the cofficients of the Landau-Ginzburg equation can be expressed in terms of the physical parameters of the crystal lattice.For these parameters,analytical ex pressions are proposed that describe their change when adding dopants in ceramic matrix composites.Perovskite barium titanate ceramics with a variety of inclusions is considered as an application example of the developed method.The obtained agreement between the analytical and experimental results for barium titanate ceramics with lanthanum/magnesium/zirconium dopants gives us hope of the applicability of the present theory to the calculation of other doped ferroelectrics as well.
基金support from the National Natural Science Foundation of China (Nos.51172166 and 51202078)the Huazhong University of Science and Technology, China (No. 01-18-185011)
文摘CaCu（3-x）FexTi4O（12）（x=0, 0.015, 0.03, 0.045, 0.06） ceramics were synthesized by sol-gel method. The electrical conduction and dielectric measurements show that the doping of a very small amount of Fe（3＋） ions greatly reduces the low-frequency dielectric constants and leakage, and enhances grain resistivity. For the doped samples, the appearance of the strong low-frequency peaks in the spectra of dielectric loss confirms that the doping of Fe（3＋） ions induces the contact-electrode effect on ceramic surface. These great changes of electrical properties may originate from the reduced amount of oxygen vacancies by doping Fe（3＋）
