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1.
0.82[0.94Bi0.5Na0.5TiO3-0.06BaTiO3]-0.18K0.5Na0.5NbO3:xZnO (BNT-BT-KNN:xZnO, x?=?0-0.40) relaxor composites were prepared and their electrical properties were investigated. The breakdown electric field increases with increasing ZnO content. For x?=?0 and x?=?0.40 samples, the maximum recoverable energy storage density is 0.74?J/cm3 and 1.03?J/cm3 while the maximum energy storage efficiency is 86.7% and 72.7% under the electric field of 9.0?kV/mm and 14.0?kV/mm, respectively. The recoverable energy storage density and efficiency of the composite vary less than 2.5% from 25?°C to 125?°C, which indicates temperature-insensitive energy storage performance. These results are discussed based on the ZnO-enhanced bulk resistivity and the ZnO-induced local electric field which suppresses the evolution of polar nanoregions.  相似文献   

2.
Novel high temperature ceramic capacitors (1??x)(Na0.5Bi0.5TiO3 ??0.15Ba0.8Ca0.2Ti0.8Zr0.2O3)??xK0.5Na0.5NbO3 were synthesized in the solid-state reaction route. The influence of K0.5Na0.5NbO3 modification on dielectric behavior, energy-storage properties, ac impedance and temperature stable dielectric performance were systematically investigated. The reduced grain size and enhanced relaxor properties are obtained with the addition of KNN. The content of x?=?0.1 exhibits a stable permittivity (~ 1630) and dielectric loss (<?0.05) over a relatively broad temperature range (66–230?°C). A variation in permittivity within ±?15% can be observed over a pretty wide temperature range of 66–450?°C. Beyond that, this ceramic shows enhanced energy-storage properties with the density (Wrec) of 0.52?J/cm3 and efficiency (η) of 80.3% at 110?kV/cm. The possible contributions of the grain and the grain boundary to the ceramic capacitance are discussed by the ac impedance spectroscopy.  相似文献   

3.
Ceramics with temperature-stable dielectric characteristics have been developed in the system: 0.6[0.85Na0.5Bi0.5TiO3-(0.15-x)Ba0.8Ca0.2TiO3-xBi(Mg0.5Ti0.5)O3]?0.4NaNbO3, x ≤ 0.15. Dielectric measurements exhibited relaxor ferroelectric characteristics with temperature-stable relative permittivity from εr~1330 ± 15% in the temperature range from ?70?°C to 215?°C and tanδ ≤ 0.02 from ?20?°C to 380?°C for x = 0 compositions. For the Bi(Mg0.5Ti0.5)O3 modified compositions the temperature range of stable relative permittivity extended from ?70?°C to 400?°C, with εr ~ 950 ± 15% and tanδ ≤ 0.02 from ?70?°C to 260?°C. Values of dc resistivity were ~ 108 Ω?m at a temperature of 300?°C and the corresponding RC constant values were in the range from 0.40 ? 0.78?s at 300?°C. All ceramic samples exhibited a linear polarisation-electric field response at maximum applied electric field of 5?kV/cm (1?kHz).  相似文献   

4.
Novel (1–x)(0.94Bi0.5Na0.5TiO3–0.06BaTiO3)–xSr0.7La0.2TiO3 ternary lead-free ceramics (BNBT–xSL, x?=?0.00–0.08) were fabricated by the widely used solid-state sintering technique. The crystal phase, microstructure, dielectric relaxation, piezoelectric, and electromechanical properties of each composition were systematically analyzed. It is found that the addition of SL has little effect on the crystal phase and grain morphology, but it can remarkably improved the relaxation property of the ceramic sample and gave rise to favourable dielectric properties in a wide range of temperatures. In addition, as the SL content increases, the ferroelectric to relaxor temperature (TF-R) is adjusted to below ambient temperature. More importantly, the decay of ferroelectric phase resulted in a significant increase in strain value: the large strain of 0.5% with normalized strain of 625?pm/V was obtained at 80kv/cm and x?=?0.04. Finally, the composition exhibited high strain of temperature insensitivity range from room temperature to 100?°C, the strain value remained above 0.4% and kept within 5%. The results are due to the coexistence of rhombohedral polar-nanoregions (PNRs) and tetragonal PNRs during the relaxor region. This result is of great importance to the developments of temperature-insensitive strain sensors and actuators.  相似文献   

5.
Multiple ion substitutions to Na0.5Bi0.5TiO3 give rise to favourable dielectric properties over the technologically important temperature range ?55?°C to 300?°C. A relative permittivity, εr,?=?1300?±?15% was recorded, with low loss tangent, tanδ?≤?0.025, for temperatures from 310?°C to 0?°C, tanδ increasing to 0.05 at ?55?°C (1?kHz) in the targeted solid solution (1–x)[0.85Na0.5Bi0.5TiO3–0.15Ba0.8Ca0.2Ti1-yZryO3]–xNaNbO3: x?=?0.3, y?=?0.2. The εr-T plots for NaNbO3 contents x?<?0.2 exhibited a frequency-dependent inflection below the temperature of a broad dielectric peak. Higher levels of niobate substitution resulted in a single peak with frequency dispersion, typical of a normal relaxor ferroelectric. Experimental trends in properties suggest that the dielectric inflection is the true relaxor dielectric peak and appears as an inflection due to overlap with an independent broad dielectric peak. Process-related cation and oxygen vacancies and their possible contributions to dielectric properties are discussed.  相似文献   

6.
The ternary (1?x)(0.8BiFeO3-0.2BaTiO3)-xK0.5Na0.5NbO3 (0?≤?x?≤?0.5) solid solutions have been successfully synthesized by a solid-state reaction route. X-ray diffraction and Rietveld refinement studies reveal the phase transition from the rhombohedral and tetragonal phases to the single tetragonal phase with x increasing. The average grain size decreases initially and then increases as x increases, whereas the remnant magnetization shows an opposite trend and reaches the maximum value of ~2.09?emu/g at x?=?0.3. An enhanced remnant polarization of ~8.6?μC/cm2 appears at x?=?0.3 due to the structure distortion and the decrement of defects. Moreover, the remanent polarization and the relative permittivity reach the maximum value of ~20.14 μC/cm2 (10?Hz) and ~644 (1?kHz) at x?=?0.5, respectively, and the corresponding dielectric loss decreases to the lowest value of ~0.022 (1?kHz). These results indicate that the properties of ternary BFO-BTO-KNN solid solutions can be modulated by adjusting the K0.5Na0.5NbO3 content to adapt to different application needs.  相似文献   

7.
The Ca0.61Nd0.26Ti1-x(Cr0.5Ta0.5)xO3 (CNT-CTx) ceramics with orthorhombic perovskite structure were prepared using the conventional solid-state method. The X-ray diffraction (XRD), Raman spectra and X-ray photoelectron spectra (XPS) were employed to investigate the correlations between crystal structure and microwave dielectric properties of CNT-CTx ceramics. The XRD results showed that all CNT-CTx samples were crystallized into the orthorhombic perovskite structure. The SEM micrographs indicated that the average grain size of samples depended on the sintering temperature. As (Cr0.5Ta0.5)4+ concentration increased, there was a significant decrease in the average grain size of samples. The short range order (SRO) structure and structural distortion of oxygen octahedra proved to exist in CNT-CTx crystals according to the analysis of Raman spectra results. The microwave dielectric properties highly depended on the full width at half maximum (FWHM) of Raman spectra, oxygen octahedra distortion, reduction of Ti4+ to Ti3+ and bond valence. At last, the CNT-CT0.05 ceramic sintered at 1420?°C for 4?h exhibited the good and stable comprehensive microwave dielectric properties: relative permittivity of 96.5, quality factor of 14,360?GHz, and temperature coefficient of resonant frequency of +153.3?ppm/°C.  相似文献   

8.
K0.5Na0.5Nb1-xTaxO3 (KNNT) (with x?=?0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830?°C for 5?h. Subsequent sintering of centimeter size pellets, 1–2?mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x?=?0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960?°C, under 50?MPa, for 5–10?min with heating rates of 100?°C/min. High relative permittivity (εr =?1027), piezoelectric charge coefficient (d33 =?160 pC/N) and piezoelectric coupling factor (kp =?46%) are obtained in spark plasma sintered K0.5Na0.5Nb1-xTaxO3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.  相似文献   

9.
The xBi(Zn2/3Nb1/3)O3–(1?x)(K0.5Na0.5)NbO3 (abbreviated as xBZN–(1?x)KNN) ceramics have been synthesized using the conventional solid‐state sintering method. The phase structure, dielectric properties and “relaxorlike” behavior of the ceramics were investigated. The 0.03BZN–0.97KNN ceramics show a broad and stable permittivity maximum near 2000 and lower dielectric loss (≤5%) at a broad temperature usage range (100°C–400°C) and the capacitance variation (ΔC/C150°C) is maintained smaller than ±15%. The 0.03BZN–0.97KNN ceramics only possess the diffuse phase transition and no frequency dispersion of dielectric permittivity, which indicates that 0.03BZN–0.97KNN ceramics is a high temperature “relaxorlike” ferroelectric ceramics. These results indicate that 0.03BZN–0.97KNN ceramics are excellent promising candidates for preparing high‐temperature multilayer ceramics capacitors.  相似文献   

10.
MnO2-doped 0.99(0.36BiScO3-0.64PbTi1-xCexO3)-0.01Bi(Zn0.5Ti0.5)O3 (BS-PTC-BZT-MnO2) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ) and suppress the decrease of piezoelectric constant (d33) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO2 ceramics are studied. The ceramics (x?=?0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ?=?1.36%, 1?kHz) and high piezoelectric constant (d33 =?360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature (TC =?422?°C), large dielectric constant (?r =?1324), and high remnant polarization (Pr =?35.1?µC/cm2) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ. In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO2 ceramics can be well applied as power electronic devices under high temperature.  相似文献   

11.
Novel ((Bi0.5Na0.5)0.94Ba0.06)1-x(K0.5Nd0.5)xTiO3(x = 0.0, 0.02, 0.04, 0.06) lead-free ceramics (BNBT–xKN) were prepared by the solid-state reaction method. The effects of A-site (K0.5Nd0.5)2+ complex-ion substitution on their phase structure, dielectric, piezoelectric, and electromechanical properties were studied. The X-ray diffraction results indicate that all compositions are located in the morphotropic phase boundary (MPB) region where the tetragonal phase coexists with the rhombohedral phase. In addition, as the KN content increases, the ferroelectric order transform to relaxor order, which is characterized by a degeneration of maximum polarization, remnant polarization and correspondingly adjusts the ferroelectric-relaxor transformation temperature (TF-R) to room temperature. Interestingly, the disruption of ferroelectric phase caused a significant improvement of strains. A maximum strain of ~ 0.52% corresponding to normalized strain of ~ 612 pm/V appeared at 85 kv/cm for the x = 0.04 composition. Particularly, the composition of x = 0.04 exhibited high electrostrains of temperature insensitivity, which remained above 0.4% and kept within 10% from ambient temperature up to 110 °C. It can be ascribed to the coexistence of non-ergodic and ergodic states in the relaxor region. As a result, the systematic investigations on the BNBT–xKN ceramics can benefit the developments of temperature-insensitive “on-off” actuators.  相似文献   

12.
Temperature‐stable relaxor dielectrics have been developed in the solid solution system: 0.45Ba0.8Ca0.2TiO3–(0.55 ? x)Bi(Mg0.5Ti0.5)O3xNaNbO3. Ceramics of composition x = 0 have a relative permittivity ?r = 950 ± 15% over a wide temperature range from +70°C to 600°C. Modification with NaNbO3 at x = 0.2 decreases the lower limiting temperature to ?70°C, but also decreases relative permittivity such that ?r ~ 600 ± 15% over the temperature range ?70°C to 500°C. For composition x = 0.3, the low‐temperature dispersion in loss tangent, tan δ, (at 1 kHz) shifts to lower temperature, giving tan δ values ≤0.02 across the temperature range ?60°C to 300°C in combination with ?r ~ 550 ± 15%. Values of dc resistivity for all samples are of the order of 1010 Ω m at 250°C and 107 Ω m at 400°C.  相似文献   

13.
Properties of lead-free Bi0.5-xLaxNa0.40K0.10Ti0.98Zr0.02O3 (x?=?0.000–0.040) ceramics were investigated. All ceramics have a pure perovskite structure. A high energy storage density (~1.00?J/cm3) at room temperature (RT) is noted for the x?=?0.030 sample, while x?=?0.020 and 0.040 samples have very high thermal stability of energy storage density of ~3% (at 75–150?°C). Furthermore, the x?=?0.030 and 0.040 samples have the highest energy storage efficiency (η) value of 94% at 125?°C with high thermal stability (η?=?84–95% at 25–150?°C). The x?=?0.005 sample has high electric field-induced strain (Smax?=?0.42%) and high normalized strain coefficient (d*33?=?Smax/Emax?=?700?pm/V) with large improvements (~200% and 163% for Smax and d*33, respectively), as compared to the based composition. This ceramic system has potentials for piezoelectric and/or energy storage density applications.  相似文献   

14.
Ceramics in the solid solution system, (1 ? x)Ba0.8Ca0.2TiO3xBi(Mg0.5Ti0.5)O3, were prepared by a conventional mixed oxide route. Single‐phase perovskite‐type X‐ray diffraction patterns were observed for compositions x < 0.6. A change from tetragonal to single‐phase cubic X‐ray patterns occurred at x ≥ 0.1. Dielectric measurements indicated relaxor behavior for x ≥ 0.1. Increasing the Bi(Mg0.5Ti0.5)O3 content improved the temperature sensitivity of relative permittivity ?r at high temperatures. At x = 0.5, a near‐plateau relative permittivity, 835 ± 40, extended across the temperature range, 65°C–550°C; the permittivity increased at x = 0.6 to 2170 ± 100 for temperatures 160°C–400°C (1 kHz). The corresponding loss tangent, tanδ, was ≤0.025 for temperatures between 100°C and 430°C for composition x = 0.5; at x = 0.6, losses increased sharply at >300°C. Comparisons of dielectric properties with other materials proposed for high‐temperature capacitor applications suggest that (1 ? x)Ba0.8Ca0.2TiO3xBi(Mg0.5Ti0.5)O3 ceramics are a promising base material for further development.  相似文献   

15.
(K0.5Na0.5)NbO3 piezoelectric ceramics can be sintered at a temperature as low as 750 °C for 5 h by incorporating Li2CO3 + Bi2O3 + ZnO as the sintering aid, whereas the conventional sintering temperature is around 1,100 °C. The optimal “soft” piezoelectric properties are obtained for ceramics sintered at 850 °C for 5 h. The dielectric permittivity (ε), piezoelectric coefficient (d 33), electromechanical coupling (k p) and mechanical quality factors (Q m) of (K, Na)NbO3 modified with 5.5 wt% sintering aids are 1,436, 90 pC/N, 0.3 and 10, respectively. These values are similar to the values obtained for (K0.5Na0.5)NbO3 ceramics sintered above 1,100 °C. The underlying mechanism for abrupt change of dielectric permittivity is explained.  相似文献   

16.
The microstructure, phase structure, ferroelectric, and dielectric properties of (1?x)Bi0.5Na0.5TiO3xNaNbO3 [(1?x)BNT‐xNN] ceramics conventionally sintered in the temperature range of 1080°C–1120°C were investigated as a candidate for capacitor dielectrics with wide temperature stability. Perovskite phase with no secondary impurity was observed by XRD measurement. With increasing NN content, (1?x)BNT‐xNN was found to gradually transform from ferroelectric (x = 0–0.05) to relaxor (x = 0.10–0.20) and then to paraelectric state (x = 0.25–0.35) at room temperature, indicated by PIE loops analysis, associated with greatly enhanced dielectric temperature stability. For the samples with x = 0.25–0.35, the temperature coefficient of capacitance (TCC) was found <11% in an ultra‐wide temperature range of ?60°C–400°C with moderate dielectric constant and low dielectric loss, promising for temperature stable capacitor applications.  相似文献   

17.
A series of temperature‐stable microwave dielectric ceramics, (1?x)(Na0.5La0.5)MoO4x(Na0.5Bi0.5)MoO4 (0.0 ≤ x ≤ 1.0) were prepared by using solid‐state reaction. All specimens can be well sintered at temperature of 580°C–680°C. Sintering behavior, phase composition, microstructures, and microwave dielectric properties of the ceramics were investigated. X‐ray diffraction results indicated that tetragonal scheelite solid solution was formed. Microwave dielectric properties showed that permittivity (εr) and temperature coefficient of resonant frequency (τf) were increased gradually, while quality factor (Q × f) values were decreased, at the x value was increased. The 0.45(Na0.5La0.5)MoO4–0.55(Na0.5Bi0.5)MoO4 ceramic sintered at 640°C with a relative permittivity of 23.1, a Q × f values of 17 500 GHz (at 9 GHz) and a near zero τf value of 0.28 ppm/°C. Far‐infrared spectra (50–1000 cm?1) study showed that complex dielectric spectra were in good agreement with the measured microwave permittivity and dielectric losses.  相似文献   

18.
Tetragonal phase (1–x)(0.875Bi0.5Na0.5TiO3–0.125BaTiO3)–xBi(Mg0.5Ti0.5)O3 lead-free ferroelectrics were designed and fabricated by a conventional solid state route. All the specimens exhibit a tetragonal perovskite structure, and undergo a phase evolution from ferroelectric P4mm to antiferroelectric relaxor P4bm as the BMT addition increases. The critical composition x?=?0.04 makes a bridge between the both tetragonal phases, and gives a large field-induced strain of 0.30% and an adequately-large electrostrictive coefficient Q33 of 0.0254?m4/C2. To be highlighted, the field-induce strain of the composition x?=?0.04 shows an almost constant value over the temperature range of 18–100?°C, illustrating a temperature-insensitive behavior, which could be attributed to the widened gap between TR–E and TF–R. The temperature-insensitive large strain of the tetragonal BNT–BT–BMT composition give a promising potential for application in precision position actuators.  相似文献   

19.
Novel lead-free [(Bi0.5Na0.5)0.94Ba0.06]0.97La0.03Ti1-x(Al0.5Nb0.5)xO3 ceramics (BNBLT-xAN) were prepared by the conventional solid state sintering method. The dielectric, ferroelectric, ac impedance and energy-storage performance were systematically investigated. Temperature dependent permittivity curves showed that relaxation properties of sintered ceramics gradually diminished with the increase of AN. The introduction of AN gave rise to a slimmer polarization hysteresis loop (P-E) and an enhanced dielectric breakdown strength (DBS). Therefore, the optimum energy-storage performance were realized at x?=?0.05 with the energy-storage density (Wrec) of 1.72?J/cm3 and energy-storage efficiency (η) of 85.6% at 105?kV/cm, accompanied with the excellent temperature stability and fatigue performance. The results demonstrated that BNBLT-xAN system was a promising lead-free candidate for energy-storage applications.  相似文献   

20.
(1-x)NBT-xBSN (0.1?≤?x?≤?0.35) ceramics were prepared by solid state methods and their energy storage properties and high-temperature capacitor applications were systematically investigated. All samples showed a perovskite structure and the structure transformed to lower symmetry orthorhombic phase (x?≥?0.1) from rhombohedral phase (x?<?0.1) to with the addition of BSN. The more addition content of BSN significantly decreases phase transition temperature Tm of NBT ceramics. The x?=?0.25 sample exhibits a stable relative permittivity of 1605?±?15% in a broad temperature range of 38?°C to 319?°C. With increasing BSN concentration, the slope of the P-E loops and the energy loss gradually decreases. When x?=?0.25, a high breakdown strength of 190?kV/cm and the maximum discharge energy density of 1.91?J/cm3 were obtained, of which the energy efficiency was as high as 86.4%. Thus, it was believed that our work could provide a significant guidance for designing the new system for energy storage.  相似文献   

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