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1.
《Journal of the European Ceramic Society》2006,26(15):3247-3251
Lead-free [Bi1−y(Na1−x−yLix)]0.5BayTiO3 (BNLB-x/y) piezoelectric ceramics were prepared by sintering the constituent oxides, and their piezoelectric and ferroelectric properties studied. The results of X-ray diffraction (XRD) suggest that Li+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 (BNT) lattices to form a solid solution with a single-phase perovskite structure. The ceramics can be well sintered at 1100–1150 °C. The introduction of Li+ and Ba2+ into Bi0.5Na0.5TiO3 significantly decreases the coercive field, Ec but maintains the large remanent polarization, Pr of the materials. The ceramics exhibit relatively good piezoelectric properties and very strong ferroelectricity: piezoelectric constant, d33 = 208 pC/N, planar electromechanical coupling factor, kp = 37.0%, remanent polarization, Pr = 38.5 μC/cm2, coercive field, Ec = 3.27 kV/mm. The depolarization temperature, Td of BNLB-0.075/0.04 ceramics is about 190 °C. 相似文献
2.
《Journal of the European Ceramic Society》2007,27(13-15):4017-4020
The site occupancies of rare earth ions for Ba-site to Ti-site were quantitatively estimated in (Ba1−x,Rx)(Ti1−x,Rx)O3 (R = Eu, Ho), (Ba1−3xEu2x)TiO3, and Ba(Ti1−2xEu2x)O3−x systems by applying the Rietveld refinement to the data obtained from the synchrotron radiation powder diffraction measurement. The occupational ratio of Ba-site to Ti-site for the larger rare earth ion (Eu) was 49/51 (x = 0.10), whereas for the smaller ion (Ho) was 9/91 (x = 0.01) in (Ba1−x,Rx)(Ti1−x,Rx)O3 system. Furthermore, the occupational ratio was greatly dependent on the Ba/Ti ratio, in (Ba1−3xEu2x)TiO3 system it was 92/8 (x = 0.03), whereas that in Ba(Ti1−2xEu2x)O3−x system was 20/80 (x = 0.01). The Curie point shifted to lower temperature effectively with increasing in the occupational ratio of rare earth ion into Ba-site. 相似文献
3.
《Journal of the European Ceramic Society》2005,25(4):489-499
The oxygen permeability of mixed-conducting Sr1−xCaxFe1−yAlyO3−δ (x=0–1.0; y=0.3–0.5) ceramics at 850–1000 °C, with an apparent activation energy of 120–206 kJ/mol, is mainly limited by the bulk ionic conduction. When the membrane thickness is 1.0 mm, the oxygen permeation fluxes under pO2 gradient of 0.21/0.021 atm vary from 3.7×10−10 mol s−1 cm−2 to 1.5×10−7 mol s−1 cm−2 at 950 °C. The maximum solubility of Al3+ cations in the perovskite lattice of SrFe1−yAlyO3−δ is approximately 40%, whilst the brownmillerite-type solid solution formation range in Sr1−xCaxFe0.5Al0.5O3−δ system corresponds to x>0.75. The oxygen ionic conductivity of SrFeO3-based perovskites decreases moderately on Al doping, but is 100–300 times higher than that of brownmillerites derived from CaFe0.5Al0.5O2.5+δ. Temperature-activated character and relatively low values of hole mobility in SrFe0.7Al0.3O3−δ, estimated from the total conductivity and Seebeck coefficient data, suggest a small-polaron mechanism of p-type electronic conduction under oxidising conditions. Reducing oxygen partial pressure results in increasing ionic conductivity and in the transition from dominant p- to n-type electronic transport, followed by decomposition. The low-pO2 stability limits of Sr1−xCaxFe1−yAlyO3−δ seem essentially independent of composition, varying between that of LaFeO3−δ and the Fe/Fe1−γO boundary. Thermal expansion coefficients of Sr1−xCaxFe1−yAlyO3−δ ceramics in air are 9×10−6 K−1 to 16×10−6 K−1 at 100–650 °C and 12×10−6 K−1 to 24×10−6 K−1 at 650–950 °C. Doping of SrFe1−yAlyO3−δ with aluminum decreases thermal expansion due to decreasing oxygen nonstoichiometry variations. 相似文献
4.
《Journal of the European Ceramic Society》2006,26(9):1629-1635
Utilizing different rare-earth cations R3+ to the Ba6 − 3xR8 + 2xTi18O54 compounds is one of effective route to tailor the dielectric constant, quality factor and temperature coefficient of frequency. In this study, densification, microstructural evolution, and microwave dielectric properties of Ba6 − 3x(Sm1 − yNdy)8 + 2xTi18O54 compound, with x ranging from 0.3 to 0.7; and y from 0 to 1.00, were investigated. The ceramics with x = 0.7 [Ba3.9(Sm1 − yNdy)9.4Ti18O54] has a higher densification compared with others, due to the formation of vacancy, in the perovskite-like tetragonal cavity of the tungsten bronze-type framework structure. Differential thermal analysis and density results show that the densification of Ba6 − 3x(SmyNd1 − y)8 + 2xTi18O54 ceramics during sintering is primarily resulting from the solid state sintering process. The phase homogeneity for the Ba6 − 3x(Sm0.5Ndo.5)8 + 2xTi18O54 system is at least extended in the range of x between 0.3 and 0.7. Combining different rare-earth cations appears not alter the single phase range in tungsten bronze-type Ba6 − 3xR8 + 2xTi18O54 ceramics. The size of the columnar-grain in the microstructure increases with increasing the Nd/Sm ratio as well as the x value. Dielectric constant changes from 91.0 to 84.2 as the x increases from 0.3 to 0.7. Variation of the Nd/Sm ratio allows one to control the τf value to the nearly 0 ppm/°C. 相似文献
5.
《Ceramics International》2015,41(7):8931-8935
The densification, microstructural evolution and microwave dielectric properties of (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics with x=0, 0.25, 0.5 and 0.75 are investigated in this study. The sintering temperature of the (Ba1−xSrx)(Mg0.5W0.5)O3 is significantly reduced from 1575 °C to 1400 °C as the x value increases from 0 to 0.25 and 0.50; this result is accompanied by the formation of the (Ba1−ySry)WO4 phase and a small quantity of second phase surrounding the grains. The grain size of the (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics is increased by raising the Sr2+ content, which significantly lowers the sintering temperature. The microstructure of the (Ba0.75Sr0.25)(Mg0.5W0.5)O3 ceramic displays the smallest average grain size of approximately 0.8 μm, with a narrow grain size distribution. Without long annealing time, very high Q×f values are obtained for the (Ba1−xSrx)(Mg0.5W0.5)O3 ceramics sintered at 1400–1575 °C for a duration of only 2 h. The (Ba0.75Sr0.25)(Mg0.5W0.5)O3 ceramic sintered at 1400 °C results in the best microwave dielectric properties, including εr of 20.6, Q×f of 152,600 GHz and τf of +24.0 ppm/°C. 相似文献
6.
《Ceramics International》2016,42(11):12843-12852
A novel lead-free, high dielectric constant, ultra-wide temperature stable dielectric ceramic Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y (0.22≤x≤0.30, y=0.015) was synthesized by the traditional solid-state reaction method. The phase composition, electric and dielectric properties of the Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3 ceramics were investigated. The P-V-L dielectric theory was introduced. And, the chemical bond energy was calculated to track the changes in micro-structure. The relationships between chemical bond energy and the macroscopic dielectric properties(εr, dielectric stability and dielectric loss) in Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramics were discussed systematically. Owing to the inhomogeneous micro-structure and the diffusion in phase transition, Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramics showed a stable permittivity (~800±15%) over a ultra-wide temperature range (−30 to 375 °C). Moreover, dielectric loss was less than 0.02 and the insulation resistance was over 1012 Ω cm. These features suggested that the Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramic could be considered as a promising candidate material for energy storage applications in harsh environment. 相似文献
7.
《Journal of the European Ceramic Society》2006,26(13):2827-2832
BaxSr1−xCo0.8Fe0.2O3−δ (0.3 ≤ x ≤ 0.7) composite oxides were prepared and characterized. The crystal structure, thermal expansion and electrical conductivity were studied by X-ray diffraction, dilatometer and four-point DC, respectively. For x ≤ 0.6 compositions, cubic perovskite structure was obtained and the lattice constant increased with increasing Ba content. Large amount of lattice oxygen was lost below 550 °C, which had significant effects on thermal and electrical properties. All the dilatometric curves had an inflection at about 350–500 °C, and thermal expansion coefficients were very high between 50 and 1000 °C with the value larger than 20 × 10−6 °C−1. The conductivity were larger than 30 S cm−1 above 500 °C except for x > 0.5 compositions. Furthermore, conductivity relaxation behaviors were also investigated at temperature 400–550 °C. Generally, Ba0.4Sr0.6Co0.8Fe0‘2O3−δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ are potential cathode materials. 相似文献
8.
《Journal of the European Ceramic Society》2006,26(14):2999-3004
Perovskites La1−xCaxAlyFe1−yO3−δ (x, y = 0 to 1) were prepared by high-temperature solid-state synthesis based on mixtures of oxides produced by colloidal milling. The XRD analysis showed that perovskites La0.5Ca0.5AlyFe1−yO3−δ with a high Fe content (1 − y = 0.8–1.0) were of orthorhombic structure, perovskites with a medium Fe content (1 − y = 0.8–0.5) were of rhombohedral structure, and perovskite with the lowest Fe content (1 − y = 0.2) were of cubic structure. Thermally programmed desorption (TPD) of oxygen revealed that chemical desorption of oxygen in the temperature range from 200 to 1000 °C had proceeded in the two desorption peaks. The low-temperature α-peak (in the 200–550 °C temperature range) was brought about by oxygen liberated from oxygen vacancies; the high-temperature β-peak (in the 550–1000 °C temperature range) corresponded to the reduction of Fe4+ to Fe3+. The chemidesorption oxygen capacity increased with increasing Ca content and decreased with increasing Al content in the perovskites. The Al3+ ions restricted, probably for kinetic reasons, the reduction of Fe4+ and the high-temperature oxygen desorption associated with it. 相似文献
9.
Darja Lisjak 《Journal of the European Ceramic Society》2012,32(12):3351-3360
The sintering of the M-type hexaferrites, AFe12O19 (A = Ba, Sr), was studied. The effects of the A cation type, the partial CuO substitution for Fe2O3 and the Fe deficiency on the sintering were examined. Samples with nominal compositions of Ba1?zSrzCuxFey?xO19?δ (z = 0 or 0.5, x = 0–1.0 and y = 11–12) were prepared with a solid-state reaction at 1000 °C. The CuO addition enhanced significantly the sintering rate of the hexaferrites at temperatures below 1100 °C, while a moderate effect on the sintering was caused by a partial substitution of Sr for Ba. The diffusion studies showed that the CuO addition enabled the reactive liquid-phase sintering of hexaferrites at 1000 °C. The relative sintered densities of the Cu-containing hexaferrite ceramics sintered at 1000 °C for 3 h were around 90%. The addition of CuO had a strong effect on the coercivity, but only a moderate effect on the magnetization of the studied ceramics. 相似文献
10.
《Ceramics International》2017,43(15):12205-12208
GeS2.5 chalcogenide glass was selected for studying effects of Ga addition on physical and structural properties. Glassy and partially crystallized samples of (100−x)GeS2.5−xGa (5 mol% ≤ x ≤ 40 mol%) were prepared, and their thermal and optical properties were characterized. With increasing Ga content (x), values of Tg and optical band gap of glasses initially increased and then decreased, showing a maximal value at x = 25 mol%, that is, with stoichiometric composition of 85.7GeS2·14.3Ga2S3. These changes were discussed and correlated to evolution of network structure, which was investigated by Raman spectra recorded in glassy matrices of (100−x)GeS2.5−xGa (5 mol% ≤ x ≤ 40 mol%). This work contributes to understanding of composition–structure–property relationship of chalcogenide glasses. 相似文献
11.
《Journal of the European Ceramic Society》2014,34(8):1981-1988
La1−x−yCexYbyNbO4 specimens with various Ce and Yb contents were prepared by solid reactions, and their crystal structure, element valence, sinterability and conductivity were investigated. LaNbO4-type single phase was formed at 1200 °C in air, and the lattice of La1−x−yCexYbyNbO4 was distorted from that of LaNbO4 to various extents, depending on the added amount of Ce and Yb. Both La and Nb remained the same valence as they are in LaNbO4; Ce4+, Ce3+ and Yb3+ were detected at room temperature. Highly densified La1−x−yCexYbyNbO4 specimens were achieved by sintering at above 1215 °C in air with conductivity 1–2 orders higher than that of pure LaNbO4 in dry air, wet air and wet 5% H2–N2 atmospheres. The conductivity changed with testing atmosphere owing to the competition of electron and proton conduction, and maximal value 4.7 × 10−4 S cm−1 was obtained in wet air at 900 °C. 相似文献
12.
《Journal of the European Ceramic Society》2007,27(8-9):3059-3062
Tungstenbronze type like Ba6−3xR8+2xTi18O54 (R = Sm or Nd) dielectric ceramics reveal high quality factor Q·f as well as high dielectric constant ɛr. We have investigated the effect of Sr substitution for Ba ions on the microwave dielectric properties of the compounds. (Ba1−αSrα)6−3xR8+2xTi18O54 (R = Sm or Nd) ceramics were prepared in the composition ranges of x = 0–0.2 and α = 0–0.312 and the microwave dielectric properties were investigated. (Ba1−αSrα)6−3xSm8+2xTi18O54, where x = 0.1 and α = 0.298, and (Ba1−αSrα)6−3xNd8+2xTi18O54, where x = 0.2, α = 0.296 revealed remarkably higher Q·f value among the solid solutions, indicating that Q·f increased with substituting Sr ions into Ba ions at the rhombic A1-site. This fact suggests that relaxation of local distortions at the A1-sites is closely related to improvement of Q·f. 相似文献
13.
《Ceramics International》2007,33(6):1105-1109
Stoichiometric and monophasic Ba1−xSrxTiO3 (x = 0.3) nanopowders were successfully prepared by the citric acid gel method using barium nitrate, strontium nitrate and tetra-n-butyl titanate as Ba, Sr, Ti sources and citric acid as complexing reagent. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared (IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the thermal decomposition behavior, the crystallization process and the particle size and morphology of the calcined powders. The results indicated that single-phase and well-crystallized Ba1−xSrxTiO3 (x = 0.3) nanopowders with particle size around 80 nm could be obtained after calcining the dried gel at 950 °C for 2 h. 相似文献
14.
《Journal of the European Ceramic Society》2014,34(10):2217-2227
The point defects and the structural and dielectric properties of Dy-doped BaTiO3 ceramics prepared at 1400 °C were investigated. The solubility of Dy in the self-compensation mode was determined to be x = 0.07 for (Ba1−xDyx)(Ti1−xDyx)O3, and no EPR signals associated with the Dy3+ Kramers ion or the Ba and Ti vacancies were detected using the electron paramagnetic resonance (EPR) technique. As x increases, the dielectric behavior changed from a first-order phase transition to a diffuse phase transition to a Y7R dielectric-temperature stability. A strong EPR signal at g = 1.974, which is rare among rare-earth-doped BaTiO3 ceramics appeared unexpectedly in the single-phase (Ba1−xDyx)Ti1−x/4O3 ceramics with deliberately designed Ti vacancies. This signal was attributed to ionized Ba vacancy defects. A preference for the self-compensation mode of Dy3+ ions is responsible for the appearance of Ba vacancies. The real formula of the nominal (Ba1−xDyx)Ti1−x/4O3 is expressed as (Ba1−xDy3x/4)(Ti1−x/4Dyx/4)O3. In addition, the defect chemistry is discussed. 相似文献
15.
《Ceramics International》2015,41(6):7897-7902
The piezoelectric and dielectric properties of the (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 (x=0.12, 0.14, 0.18, 0.20 and 0.30) lead-free ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintered at 1170 °C in air. Scanning electron microscopy indicated that increasing x from 0.12 to 0.30 causes a decrease in the grain size. The (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 ceramics shows a homogeneous microstructure and excellent dielectric and piezoelectric properties. Specimens with optimum composition showed a piezoelectric charge constant d33 of 166 pC/N, an electromechanical coupling factor kp of 0.5, a dielectric constant εr of 1591.32 at 1 kHz and generated power output of 37.49 nW/cm2. 相似文献
16.
《Journal of the European Ceramic Society》2017,37(4):1421-1427
In this work, we report the polymorphic phase transitions(PPT) in ferroelectric Ba0.95Sr0.05ZrxTi(1-x)O3 (BSZT, x = 0.01–0.10) ceramics synthesized by using a solid-state reaction method. The doping elements and composition ratios were selected to create adjoining PPT phase boundaries near room temperature, hence to achieve a broadened peak of piezoelectric performance with respect to composition. The temperature-composition phase diagram was constructed and the effects of PPT on the electromechanical and ferroelectric properties of the ceramics were investigated. It was revealed that the two adjacent PPT regions at room temperature showed different characteristics in property enhancement. However, due to the proximity of the phase boundaries, Ba0.95Sr0.05ZrxTi(1-x)O3 ceramics in a fairly broad range of compositions (0.02 ≤ x ≤ 0.07) showed excellent piezoelectric properties, including a large piezoelectric constant (312 pC/N ≤ d33 ≤ 365 pC/N) and a high electromechanical coupling coefficient kp (0.42 ≤ kp ≤ 0.49). 相似文献
17.
Jean-François Trelcat Christian Courtois Mohamed Rguiti Anne Leriche Paul-Henri Duvigneaud Tiriana Segato 《Ceramics International》2012,38(4):2823-2827
Lead-free x Bi0.5Na0.5TiO3–y BaTiO3–z Bi0.5K0.5TiO3 piezoelectric ceramics were synthesized by a conventional solid state reaction method. The microstructure, ferroelectric and piezoelectric properties of the ceramics were investigated. Structure measurements by X-ray diffraction with Rietveld refinement have allowed us to specify more precisely the morphotropic phase boundary (MPB) in this system. For (1 ? x) BNT–x BT solid solution ceramics, the 0.94 BNT–0.06 BT morphotropic composition shows the higher values with d33 = 170 pC/N, kp = 0.35 and kt = 0.53. In the case of (1 ? x) BNT–x BKT compositions, the d33, kp and kt are, respectively, 137 pC/N, 0.39 and 0.54 for the 0.80 BNT–0.20 BKT ceramic. On the other hand, the ternary 0.865 BNT–0.035 BT–0.100 BKT morphotropic composition shows high piezoelectric constant and electromechanical coupling factors (d33 = 133 pC/N, kp = 0.26 and kt = 0.57). 相似文献
18.
(1?x?y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiFeO3 (BNKFT-x/y with 0.12≤x≤0.24, 0≤y≤0.07) lead-free piezoelectric ceramics have been prepared by the combustion technique. The effects of amounts of x and y on structures and electrical properties were examined. Powders and ceramics can be well calcined and sintered at 750 °C for 2 h and 1025–1050 °C, respectively. The results indicated that the crystalline structure and microstructure changed with the increase of x and y concentrations. XRD results of BNKFT-x/0.03 and BNKFT-0.18/y ceramics with 0.12≤x≤0.24 and 0≤y≤0.07 showed the rhombohedral–tetragonal morphotropic phase boundary (MPB). The addition of y caused a promoted grain growth while the addition of x suppressed the grain growth. The highest density (ρ=5.85 g/cm3), superior dielectric properties at Tc (εr=7846 and tan δ=0.02), remnant polarization measured at 40 kV/cm (Pr = 20.1 μC/cm2) and piezoelectric coefficient (d33=213 pC/N) were obtained for x=0.18 and y=0.03. 相似文献
19.
《Journal of the European Ceramic Society》2007,27(13-15):3987-3990
The Ba5Nb4O15 ceramic offers attractive dielectric properties (ɛr ∼ 39, tan(δ) < 10−3, ρi ∼ 1012 Ω cm) but exhibits a high permittivity temperature coefficient (τɛ ∼ −171 ppm °C−1). In order to tune this parameter, substitutions on the Ba and Nb sites by, respectively, Mg, Ca, Sr and V, Ta, Sn have been investigated. Two interesting formulations have been identified, Ba2.5Mg2.5Nb4O15 and Ba5Nb3SnO14.5 as nominal compositions, with temperature coefficients of −44 and −30 ppm °C−1, respectively. More attention has been paid to the Ba5Nb3SnO14.5 compound (named 504Sn25) in which BaSnO3 has been clearly identified as a secondary phase. BaSnO3, having a positive and very high temperature coefficient (+393 ppm °C−1), seems to be responsible for the τɛ lowering of 504Sn25. Furthermore B2O3 addition as sintering aid has been successfully investigated for increasing the Ba5Nb3SnO14.5 sample density. In terms of dielectric properties, it induces an increase of the permittivity and of the insulating resistivity, while the control of τɛ is maintained. Finally, the formulation 504Sn25 + 15 mol% B2O3 sintered at 1200 °C has a value of 17.8 as dielectric constant and −1 ppm °C−1 as τɛ value, that evidences the potentiality of this material to be used as temperature stable capacitor. 相似文献
20.
Crystal structure and microwave dielectric properties of (Ba1−αSrα)6−3xSm8+2xTi18O54 solid solutions
《Journal of the European Ceramic Society》2006,26(10-11):2035-2038
The tungstenbronze-type-like (Ba1−αSrα)6−3xR8+2xTi18O54 (R = rare earth) solid solutions have been studied. Microwave dielectric properties of these solid solutions link to the substitution of large cations such as Ba ions by small Sr ions. In these solid solutions for x = 0, the quality factor (Q·f) exibits extremely low due to the inner strain resulting by the occupation of large Ba ions at relatively small A1-sites. However, dielectric constant (ɛr) of this composition show a high value. In this paper, improvement of quality factor (Q·f) by substituting small Sr ions for Ba ions in (Ba1−αSrα)6−3xSm8+2xTi18O54 solid solutions, where x = 0, is reported. In addition, the relationship between crystal structure and microwave dielectric properties is discussed from the viewpoint of structural formula and occupational state of large cations such as Ba, Sr and Sm in A1-sites. 相似文献