Perovskite type ceramics (Ba0.9Mg0.1)(SnxZr0.4-xTi0.6)O3 (with x = 0.01, 0.02, 0.03 and 0.04) relaxor composition prepared through solid state reaction route and calcinated at temperature is 1150°C for 5 hrs with...Perovskite type ceramics (Ba0.9Mg0.1)(SnxZr0.4-xTi0.6)O3 (with x = 0.01, 0.02, 0.03 and 0.04) relaxor composition prepared through solid state reaction route and calcinated at temperature is 1150°C for 5 hrs with intermediate mixing. The room temperature XRD study suggests that all the samples have the single phase cubic symmetry with space group pm 3 m. The pellets were sintered at 1500°C for 4 hrs. Scanning Electron Microscope (SEM) observations revealed enhanced micro structural uniformity and retarded grain growth with decreasing Sn content. The dielectric measurements at constant frequency show that dielectric constant increases with Sn content. Loss factor and dielectric constant decreased with increasing frequency but at very high frequencies it was independent.展开更多
Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. F...Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors展开更多
The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD,SEM and TEM. The dielectric properties of the ceramics were also me...The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD,SEM and TEM. The dielectric properties of the ceramics were also measured. The influences of calcination temperature and Mn concentration on the microstructure,dielectric properties and phase composition of BaTiO3 nano-powders and ceramics were discussed. The results indicated that the BaTiO3-based powders doped with 1.0mol% Mn were mainly in cubic BaTiO3 phase,but the tetragonal phase became more evident when the calcination temperature increased. After sintering,Mn-doped ceramics were mainly composed of cubic BaTiO3. Specially,a new phase of hexagonal crystal BaTiO3 and BaMnO3 existed in the ceramics doped with 5.0mol% Mn and the ceramic grains were in ‘clintheriform’. The structure of ‘clintheriform’ led to the poor densification of ceramics,reducing the dielectric constant obviously. The dielectric constants of BaTiO3 ceramics first increased and then decreased as the Mn concentration increased. The room temperature dielectric constant was 2290 and the lowest dielectric loss was 0.004 when the Mn concentration was 0.5mol%.展开更多
Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction m...Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM） and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 decreased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 ℃ could also be obtained. The piezoelectric constant （d33）, the relative permit-tivity （εr） and the planar electromechanical coupling factor （kp） of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss （tanδ） decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount （x） was 0.2 wt.%, the BCTZ ceramics doped with Li2CO3 （0.6 wt.%） and sintered at 1050 ℃ possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.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
文摘Perovskite type ceramics (Ba0.9Mg0.1)(SnxZr0.4-xTi0.6)O3 (with x = 0.01, 0.02, 0.03 and 0.04) relaxor composition prepared through solid state reaction route and calcinated at temperature is 1150°C for 5 hrs with intermediate mixing. The room temperature XRD study suggests that all the samples have the single phase cubic symmetry with space group pm 3 m. The pellets were sintered at 1500°C for 4 hrs. Scanning Electron Microscope (SEM) observations revealed enhanced micro structural uniformity and retarded grain growth with decreasing Sn content. The dielectric measurements at constant frequency show that dielectric constant increases with Sn content. Loss factor and dielectric constant decreased with increasing frequency but at very high frequencies it was independent.
文摘Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors
文摘The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD,SEM and TEM. The dielectric properties of the ceramics were also measured. The influences of calcination temperature and Mn concentration on the microstructure,dielectric properties and phase composition of BaTiO3 nano-powders and ceramics were discussed. The results indicated that the BaTiO3-based powders doped with 1.0mol% Mn were mainly in cubic BaTiO3 phase,but the tetragonal phase became more evident when the calcination temperature increased. After sintering,Mn-doped ceramics were mainly composed of cubic BaTiO3. Specially,a new phase of hexagonal crystal BaTiO3 and BaMnO3 existed in the ceramics doped with 5.0mol% Mn and the ceramic grains were in ‘clintheriform’. The structure of ‘clintheriform’ led to the poor densification of ceramics,reducing the dielectric constant obviously. The dielectric constants of BaTiO3 ceramics first increased and then decreased as the Mn concentration increased. The room temperature dielectric constant was 2290 and the lowest dielectric loss was 0.004 when the Mn concentration was 0.5mol%.
基金supported by Project of Combination of Producing,Learning and Studying of Guangdong Province and Education Department(2011B090400027)
文摘Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM） and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 decreased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 ℃ could also be obtained. The piezoelectric constant （d33）, the relative permit-tivity （εr） and the planar electromechanical coupling factor （kp） of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss （tanδ） decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount （x） was 0.2 wt.%, the BCTZ ceramics doped with Li2CO3 （0.6 wt.%） and sintered at 1050 ℃ possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.
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.
