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1.
Uniform and relatively dense BaTiO3 thick films of 1–5 μm were prepared by an electrophoretic deposition process using submicrometer BaTiO3 powders (mean particle size: ∼0.2 μm). Two different BaTiO3 powders and solvent media were used to investigate the film quality and thickness control. The surface charge mechanism of BaTiO3 particles was explained according to the observed results. The microstructures were examined by means of SEM. The experimental results show that the thickness could be controlled independently of suspension concentration by keeping a constant applied voltage and a constant current drop in a given suspension. BaTiO3 thick films have good insulation resistance and dielectric properties such as a dielectric constant and a dissipation factor that are compatible with the data from conventional tape-cast BaTiO3 thin layers.  相似文献   

2.
A conducting 8-μm-thick LaNiO3 (LNO) film was deposited on a Ti substrate by aerosol deposition for use as a diffusion barrier between a lead zirconate titanate (PZT) and a Ti substrate during postannealing. The deposited 20-μm-thick PZT films were annealed at 800°C. The PZT film deposited without LNO was cracked and partially detached from the substrate after postannealing, presumably due to a severe reaction with the Ti substrate, while no significant reactions were observed when the LNO buffer layer was used. The remnant polarization and relative dielectric constant of the 20-μm-thick annealed PZT films deposited on the LNO-buffered Ti substrate were 43 μC/cm2 and 1010, respectively.  相似文献   

3.
X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and an impedance analyzer were used to examine the Nb–Co codoping effects on the densification, crystalline phase, microstructure development, and dielectric–temperature characteristics of BaTiO3–(Bi0.5Na0.5)TiO3 ceramics. The results indicate that the Curie temperature shifted to a higher temperature (above 140°C) by adding BNT. The dielectric constant–temperature (ɛ– T ) curve broadened at the Curie temperature due to the small grain size (0.3–0.4 μm). A core-shell structure was developed, which is helpful to flatten the ɛ– T curve of BaTiO3 ceramics at high temperatures.  相似文献   

4.
The effects of different sintering procedures on the preparation of antiferroelectric thick films and the structure–property relations in these films were studied. An acetic acid-based sol–gel processing with multistep annealing and suitable lead oxide overcoat layers was developed to fabricate both niobium-doped and lanthanum-doped lead zirconate titanate stannate antiferroelectric thick films. The 5-μm-thick Pb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)0.98O3 films demonstrate typical square hysteresis loops with a maximum polarization of 40 μC/cm2, zero remanent polarization, an antiferroelectric-to-ferroelectric phase transition field of 153 kV/cm, and a ferroelectric-to-antiferroelectric phase transition field of 97 kV/cm. The dielectric constant and dielectric loss are 283 and 1.7%, respectively. The 5-μm-thick Pb0.97La0.02(Zr0.65Sn0.31Ti0.04)O3 films display typical slanted hysteresis loops with very small hysteresis, a maximum polarization of 35.0 μC/cm2, and zero remanent polarization. The dielectric constant and dielectric loss are 434 and 2.0%, respectively.  相似文献   

5.
The influence of La2O3 doped on the microstructure and dielectric properties, including the phase structure, temperature dependence of permittivity, and the hysteresis loop of BaTiO3–Nb2O5–Fe2O3 (BTNF) materials has been investigated in X-ray diffraction, SEM, and LCR analyzer, respectively. Experiments revealed that incorporation of proper content of La2O3 basically soluted in the lattice of BaTiO3 and can control the grain-growth, reduce the dielectric loss of the BTNF materials. The development of microstructure promoted by the additives can result in the improvement of the dielectric constant. When the doping concentration of La2O3 was 3.846 wt%, the relative dielectric constant of the sample sintered at 1280°C only for 2 h could reach 4308, and improve the dielectric-temperature characteristics markedly. As a result, a novel Y5P can be achieved in the BTNF ceramics, which is very promising for practical use in Y5P multilayer ceramic capacitors.  相似文献   

6.
Ferroelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN-PT) thin films were deposited on ZrO2/SiO2/silicon substrates using a chemical-solution-deposition method. Using a thin PZT film as a seed layer for the PMN-PT films, phase-pure perovskite PMN-PT could be obtained via rapid thermal annealing at 750°C for 60 s. The electrical properties of in-plane polarized thin films were characterized using interdigitated electrode arrays on the film surface. Ferroelectric hysteresis loops are observed with much larger remanent polarizations (∼24 μC/cm2) than for through-the-thickness polarized PMN-PT thin films (10–12 μC/cm2) deposited on Pt/Ti/Si substrates. For a finger spacing of 20 μm, the piezoelectric voltage sensitivity of in–plane polarized PMN-PT thin films was ∼20 times higher than that of through-the-thickness polarized PMN-PT thin films.  相似文献   

7.
Polycrystalline barium titanate fired in nitrogen at 1300° to 1400°C accommodates up to 3 mole % UO2 in solid solution; its structure is then cubic at room temperature. With BaUO3 additions the structure becomes disordered and quasi-cubic. In air, about 1 mole % UO2 goes into solid solution in BaTiO3 but the structure remains tetragonal. Diffraction peaks of a new phase, possibly a ternary oxide of barium, uranium, and titanium, appear in patterns of specimens containing more than 2 mole % UO2. The dielectric constant of BaTiO3 ceramics fired in air, steam, or oxygen increases with up to about 0.5 mole % UO2 but declines rapidly above this level. The dielectric constant of BaUO3 is about two orders of magnitude lower than that of BaTiO3, and additions of BaUO3 invariably lower the dielectric constant of BaTiO3.  相似文献   

8.
Perovskite solid solution in the (1− x )[0.4BiScO3–0.6BaTiO3]+ x (K1/2Bi1/2)TiO3 [BSBT–KBT x ] system was synthesized using conventional sintering and hot-isostatic pressing. Dielectric properties of BSBT ceramics with different dopant levels of KBT were characterized as a function of temperature and frequency for potential use of high-temperature capacitors. The BSBT ceramics with KBT exhibited high dielectric permittivities (ɛr) (>1700 at RT) and low dielectric loss over the temperature range from 100° to 300°C, with flat temperature coefficients of permittivity (TCɛs). In addition, BSBT ceramics with increasing KBT were observed to possess dielectric relaxation characteristics at temperatures (>RT) as observed in lead-based relaxors. Furthermore, high energy densities, being on the order of 4.0 J/cm3 at 220 kV/cm was observed for the BSBT–KBT20 ceramics from the electric-field polarization behavior.  相似文献   

9.
The effects of Dy doping and sintering parameters on the properties of BaTiO3 ceramics were studied. The average grain size decreases with increasing Dy content and is controlled at ∼1.5 μ m by 0.8 at.% Dy. The Curie temperature change, associated with ≤1.2 at.% Dy, is <3°C. The dielectric constant is ∼2600 for specimens doped with 0.8 at.% Dy, calcined at 1200°C, and sintered at 1450°C. The dielectric constant variation with ambient temperature is much less than that of conventional BaTiO3 ceramics. Lattice constant c decreases with increasing Dy concentration whereas a increases slightly. The effects of grain size on dielectric constant, lattice parameters, and linear thermal expansion coefficient are more pronounced than the chemical effects of Dy doping in the ferroelectric state, whereas in the paraelectric state, these characteristics are almost independent of grain size as well as Dy concentration. The decrease in the frequency of occurrence of 90° twins with decreasing grain size implies that internal stress, which develops when BaTiO3 ceramics are cooled below Tc , strongly influences the effects of grain size.  相似文献   

10.
The use of Pb(Zn1/3Nb2/3)O3 ceramics is restricted by the formation of a pyrochlore phase detrimental to both dielectric and piezoelectric properties. Recently it has been shown that a 6 mol% addition of BaTiO3 to PZN suppresses the formation of pyrochlore phase. Phase relations and dielectric properties of ceramics in the PZN-BT-PT system are reported here. Compositions with the perovskite structure, having high dielectric constant and low temperature coefficient of capacitance, have been identified.  相似文献   

11.
Ba1– x Pb x TiO3 powder with a fixed composition was prepared by the reaction of BaTiO3 powders with molten PbCl2at various PbCl2/BaTiO3 molar ratios at 600° and 800°C in a nitrogen atmosphere. When 0.1 μm powder was used, the reaction was finished when x = 0.9. Two phases of BaTiO3and a solid solution of Ba1– x Pb x TiO3 coexisted, but the final phase gave a solid solution of Ba1– x Pb x TiO3 at 800°C. When 0.5 μm powder was used, the two phases coexisted in the products at 600°C at PbCl2/BaTiO3= 1.0. A sintered compact of Ba1– x Pb x TiO3 powders solid solution was prepared by hot isostatic pressing, and its dielectric constant was measured in the temperature range 20°–550°C.  相似文献   

12.
In this study, the effect of SiO2 doping on the sintering behavior, microstructure, and dielectric properties of BaTiO3-based ceramics was investigated. Silica was added to (Ba0.96Ca0.04)(Ti0.85Zr0.15)O3 (BCTZ) powder prepared using the solid-state method. SiO2-doped BCTZ ceramics with a high density and a uniform grain size were obtained and sintered at 1220°C in a reducing atmosphere. A second phase (BaTiSiO5) existed in samples when SiO2 was added in excess of 1%. The amount of the second phases was observed to increase as the number of SiO2 additives increased. It was found that BCTZ ceramics sintered with SiO2 are helpful in reducing the sintering temperature for a typical thick film and MLCC applications. However, there were disadvantageous effects on the dielectric properties with mere addition of SiO2 addition (3% and 5%) due to higher formation of BaTiSiO5. Doping with a small amount of silica can improve the sintering and dielectric properties of BCTZ ceramics. In addition, to understand the effect of the BaTiSiO5 phase on the dielectric properties of BCTZ ceramics, the BaTiSiO5 composition was synthesized from individual BaCO3, TiO2, and SiO2 powders using conventional solid-state methods. X-ray diffraction results show the presence of mainly the crystalline phase, BaTiSiO5, in the sintered ceramics.  相似文献   

13.
The dielectric properties, including the DC breakdown strength, of 1 mol% Nb5+-doped BaTiO3 ceramics with different quantities of excess TiO2 have been investigated. The breakdown strength was found to decrease with increasing TiO2 content, but could not be readily explained by relative density and grain size effects. The decrease in the breakdown strength from a stoichiometric BaTiO3 composition to samples with excess TiO2 is believed to be due to the field enhancement effect (up to a factor of 1.40) at the BaTiO3 matrix because of the presence of a Ba6Ti17O40 second phase. The thermal expansion coefficient mismatch between the BaTiO3 matrix phase and the Ba6Ti17O40 phase may also result in a low breakdown strength. The dielectric properties of the pure Ba6Ti17O40 phase were also investigated and are reported herein.  相似文献   

14.
Nanograined BaTiO3 ceramics prepared from 40-nm-size BaTiO3 nanopowders exhibited the cubic as well as the tetragonal phase, while nanograined BaTiO3 ceramics prepared from BaTiO3 nanopowders coated with Mn had only the tetragonal phase. The dielectric constant of the latter was 10 times larger than that of the former; the latter exhibited PTCR behavior with a resistivity jump ratio of about 5.0 × 104. These physical properties of the BaTiO3 ceramics appeared to be significantly affected by the strain near grain boundaries; such strain resulted in a phase transition from the cubic to the tetragonal phase in the nanograined BaTiO3 ceramics, even though the grain size was about 40 nm.  相似文献   

15.
BaTiO3 ceramics with grain sizes from 0.6 to 60 μm and relative densities of 89% to 92% were prepared by hot forging and conventional sintering from very pure-oxalate-derived powder. The aging of both the dielectric constant and the dielectric loss was examined at weak and strong fields with respect to grain size and frequency. It was concluded that the main aging mechanism is the aging of hysteretic domain wall motion for coarse-grained ceramics. At grain size of less than 1 μm, the lack of frequency and E AC dependence, along with a lower aging rate, suggests that domain motions or hysteretic domain wall motions are restricted in finegrained ceramic BaTiO3 and contribute little to the aging.  相似文献   

16.
Piezoelectric ceramics Na1− x Ba x Nb1− x Ti x O3 with low BaTiO3 concentrations x have been prepared by the solid-state reaction method, and their ferroelectric and piezoelectric properties have been studied. The ceramics are classic ferroelectrics when x ≤0.10, and the ferroelectric–paraelectric phase transition becomes diffusive when x ≥0.15. A low doping level of BaTiO3 changes the NaNbO3 ceramics from antiferroelectric to ferroelectric. With the increase in BaTiO3 doping level, the Curie temperature of ceramics decreases linearly and the remnant polarization and coercive field also decrease, while their dielectric constant increases. Na0.9Ba0.1Nb0.9Ti0.1O3 ceramics show the largest piezoelectric constant d 33 (147 pC/N) and good sinterability, suggesting that it is a good candidate for lead-free piezoelectric ceramics.  相似文献   

17.
BaTiO3 nanofibers were prepared by electrospinning. The morphology of synthesized BaTiO3 nanofibers was investigated under different heat treatment conditions. The phase transformations in BaTiO3 nanofibers were monitored using Raman spectroscopy. It has been found that the Curie temperature of BaTiO3 nanofibers increased to 220°C, which is notably higher than the bulk BaTiO3 ceramics.  相似文献   

18.
Micron-scale platelet barium titanate was synthesized using a twostep molten salt and topochemical technique. Plate-like BaBi4Ti4O15 was first synthesized as a precursor by molten salt synthesis. Then, Bi3+ in the precursor was replaced by Ba2+ and formed perovskite-structure BaTiO3 through a topochemical reaction. The BaTiO3 single crystals have an average size of 5–10 μm and a thickness of 0.5 μm. The purpose of this article is to control the particle shape with desired structure. High aspect ratio BaTiO3 platelets are suitable templates to obtain textured ceramics (especially Pb(Mg1/3Nb2/3)O3–32.5PbTiO3) by the templated grain growth process.  相似文献   

19.
Effects of grain size and grain growth in Nb-doped BaTiO3 on temperature and frequency dependencies of the dielectric constant were investigated. When 0.65 μm powder is sintered to an average grain size of 1 μm, two dielectric constant peaks indicate the presence of Nb-free BaTiO3 and of Nb-containing material. Single peaks are observed above room temperature after additional grain growth or when 0.07 μm powder is sintered to an average grain size of 1 μm. The Curie point of pure BaTiO3 with 1 μm grains is 4 to 6°C lower than that of material with grains >10 μm. Thermodynamically, this behavior is accounted for by a phase inversion stress ∼ the room-temperature stress.  相似文献   

20.
Textured 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 (NBT–6BT) ceramics were fabricated by templated grain growth (TGG) using anisotropically shaped Na0.5Bi0.5TiO3 (NBT) templates. Platelet NBT was synthesized by the topochemical technique, using precursor Na0.5Bi4.5Ti4O15 (NBIT). The NBT particles have an average length of 10–15 μm and a thickness of 1 μm, which are suitable templates for obtaining textured ceramics (especially NBT-based ceramics) by the TGG process. This study revealed that the NBT templates are effective in inducing grain orientation in NBT–6BT ceramics. For NBT–6BT ceramics textured with 5 vol% NBT templates, a Lotgering factor of 0.87 and a d 33 of 299 pC/N are given.  相似文献   

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