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1.
Wei Zhao Jing Ya Ying Xin Lie E Dan Zhao Heping Zhou 《Journal of the American Ceramic Society》2009,92(7):1607-1609
Textured 0.94Na0.5 Bi0.5 TiO3 –0.06BaTiO3 (NBT–6BT) ceramics were fabricated by templated grain growth (TGG) using anisotropically shaped Na0.5 Bi0.5 TiO3 (NBT) templates. Platelet NBT was synthesized by the topochemical technique, using precursor Na0.5 Bi4.5 Ti4 O15 (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
2.
J. T. Zeng K. W. Kwok W. K. Tam H. Y. Tian X. P. Jiang H. L. W. Chan 《Journal of the American Ceramic Society》2006,89(12):3850-3853
Large plate-like Na0.5 Bi0.5 TiO3 (NBT) templates have been successfully synthesized from bismuth layer-structured ferroelectric Na0.5 Bi4.5 Ti4 O15 (NBIT) particles by the topochemical method. Because of the highly anisotropic structure, plate-like NBIT particles were first synthesized by the molten-salt process. After the topochemical reaction with the complementary reactants (Na2 CO3 , and TiO2 ) in NaCl flux, the layer-structured NBIT particles were transformed to the perovskite NBT templates. The resulting NBT templates are large and of plate-like shape. Our results also reveal that they are more effective in inducing grain orientation in the BNKT-BT ceramics as compared with BIT templates. For a BNKT-BT ceramic textured with 20 wt% of NBT templates, it exhibits a very high degree of grain orientation and gives a large Lotgering factor of 0.89. 相似文献
3.
Wei Zhao Heping Zhou Yongke Yan Dan Liu 《Journal of the American Ceramic Society》2008,91(4):1322-1325
Plate-like Na0.5 Bi0.5 TiO3 (NBT) particles with perovskite structure were synthesized by topochemical microcrystal conversion from plate-like particles of layer-structured Na0.5 Bi4.5 Ti4 O15 (NBIT) at 950°C in NaCl molten salt. As the precursors of NBT, plate-like NBIT particles were first synthesized by molten salt process by the reaction of Bi4 Ti3 O12 , Na2 CO3 , and TiO2 . After the topochemical reactions, layer-structured NBIT particles were transformed to the perovskite NBT platelets. NBT particles with a thickness of approximately 0.5 μm and a length of 10–15 μm retained the morphology feature of the precursor. High-aspect-ratio NBT platelets are suitable templates to obtain textured ceramics (especially NBT-based ceramics) by (reactive) template grain growth process. 相似文献
4.
Sodium bismuth titanates Na1/2 Bi1/2 TiO3 (NBT) doped with 0–3 wt% Er2 O3 were prepared by the conventional solid-state reaction method. The X-ray diffraction results revealed that the sintered Er-doped NBT ceramics exhibited a pure perovskite structure with Er3+ concentrations ranging from 0 to 1 wt%. At a low Er2 O3 concentration, the Er-doped NBT ceramics showed enhanced electrical properties with dielectric constant ɛ33 T /ɛ0 =636, a low dielectric dissipation factor (tan δ=3.3%), a low coercive field ( E c =4.56 kV/mm), and a high piezoelectric constant ( d 33 =75 pC/N). The relationship between the composition and properties of Er-doped NBT ceramics has been discussed. 相似文献
5.
The sintering and electrical characteristics of La-modified Na1/2 Bi1/2 TiO3 (NBT) was investigated from a defect structure viewpoint. To reveal the role of cation vacancies, two series of ceramics, with different cation vacancies, were processed to compensate the excess positive charge of lanthanum ions. In a region of complete solid solution, the grain size of NBLT-B {[(Na0.5 Bi0.5 )1− x La x ]Ti1−0.25 x O3 } was smaller than that of NBLT-A {[(Na0.5 Bi0.5 )1−1.5 x La x ]TiO3 } and densification was enhanced more effectively in NBLT-B. With the aid of thermoelectric power, electric conductivity, and electrotransport measurements, it was found that different sintering behaviors between NBLT-A and NBLT-B specimens were related to the change in the type of cation vacancies present and that lanthanum ion–cation vacancy pairs played an important role in reducing the grain growth and enhancing the densification process. 相似文献
6.
PbTiO3 -doped sodium bismuth titanate (Na1/2 Bi1/2 )1− x Pb x TiO3 of perovskite structure is one of the best-known piezoelectrics/ferroelectrics. However, it has not been properly investigated in any thin-film forms. In this study, the dielectric properties of (Na1/2 Bi1/2 )0.87 Pb0.13 TiO3 thin films synthesized via a sol–gel route were investigated. They exhibit a strong frequency dispersion of the dielectric permittivity at relatively high frequencies, which is shifted to lower frequencies with increasing temperature. The electrical behavior can be fitted using Jonscher's universal law for dielectric relaxation. The peculiar dielectric behaviors observed can be ascribed to the coexistence of two different dielectric phases in the films, which is believed to be associated with the growth of the local Pb2+ TiO3 nanoclusters upon substitution of Pb2+ for Na+ /Bi3+ in the (Na1/2 Bi1/2 )1− x Pb x TiO3 films. 相似文献
7.
Jakob König Botjan Janar Danilo Suvorov 《Journal of the American Ceramic Society》2007,90(11):3621-3627
X-ray diffraction analyses and scanning electron microscopy revealed that Na0.5 Bi0.5 TiO3 (NBT) and NaTaO3 (NTa) form solid solutions across the whole concentration range. With increasing NTa content the symmetry of the solid solutions gradually changed from rhombohedral, on the NBT-rich side, to orthorhombic, on the NTa-rich side. No morphotropic phase boundary was found between these phases. With increasing NTa content, the perovskite lattice parameter ( a p ) and the sintering temperature increase, whereas the grain size decreases. In the case of pure NTa, ceramics with a secondary phase were obtained, identified as Na2 Ta8 O21 , which was formed during the sintering process. A study of the dielectric properties showed that with an increasing concentration of NTa, there was a reduction and broadening of the permittivity maximum, a reduction of the temperatures of the dielectric anomalies, and a reduction of the dielectric losses. 相似文献
8.
Yuanhua Lin Ce-Wen Nan Jianfei Wang Gang Liu Junbo Wu Ning Cai 《Journal of the American Ceramic Society》2004,87(4):742-745
The dielectric properties of Na0.5 Bi0.5 TiO3 (NBT) -based composites incorporating silver particles prepared by sintering at a low temperature of ∼900°C are reported. The dielectric constant increases with the amount of metal silver particles in the measured frequency range (150 Hz to 1 MHz), and could be enhanced up to ∼20 times higher than that of pure NBT ceramics, which was ascribed to the effective electric fields developed between the dispersed particles in the matrix and the percolation effect. Further investigation revealed that the dielectric constant of the composites has weak frequency and temperature dependence (−50°C to +50°C). 相似文献
9.
Subsolidus phase relations in the system Na2 O-Bi2 O3 -TiO2 at 1000°C were investigated by solid-state reaction techniques and X-ray diffraction methods. Five ternary compounds were observed in the system: Na0.5 Bi4.5 Ti4 O15 ; Na0.5 Bi0.5 TiO3 ; a cubic pyrochlore solid solution composed of xNa2 O.25Bi2 O3 .(75−;x) TiO2 where x is 2.5 to 3.75; a new compound Na0.5 Bi8.5 Ti7 O27 indexed with the orthorhombic cell of a = 5.45, b = 5.42, and c = 36.8 Å; and an unidentified phase with the probable composition NaBiTi6 O14 . 相似文献
10.
Matja Spreitzer Botjan Janar Danilo Suvorov 《International Journal of Applied Ceramic Technology》2009,6(2):302-311
The phase relations and the mechanism of solid-state synthesis for the Na0.5 Bi0.5 TiO3 –Li3 x La(2/3)− x □(1/3)−2 x TiO3 system were investigated using X-ray powder diffraction, scanning electron microscopy, and thermal analysis. The study revealed that the extent of the homogeneity range—which is related to the A-site substitution between (Na0.5 Bi0.5 )2+ and (Li3 x La(2/3)− x □(1/3)−2 x )2+ pseudo cations of a perovskite structure—depends strongly on the ordering of the (Li3 x La(2/3)− x □(1/3)−2 x )2+ species. The solid-state reaction of the compounds in the homogeneity range is completed only after multiple high-temperature firings. However, the system is also subjected to a slow thermal decomposition; this is particularly so for the compounds with a high × value and an increased Li3 x La(2/3)− x □(1/3)−2 x TiO3 concentration. 相似文献
11.
Yu-Dong Hou Lei Hou Ting-Ting Zhang Man-Kang Zhu Hao Wang Hui Yan 《Journal of the American Ceramic Society》2007,90(6):1738-1743
The sol–gel–hydrothermal processing of (Na0.8 K0.2 )0.5 Bi0.5 TiO3 (NKBT) nanowires as well as their densification behavior were investigated. The morphology and structure analyses indicated that the sol–gel–hydrothermal route led to the formation of phase-pure perovskite NKBT nanowires with diameters of 50–80 nm and lengths of 1.5–2 μm, and the processing temperature was as low as 160°C, but the conventional sol–gel route tended to lead to the formation of NKBT agglomerated porous structured nanopowders, and the processing temperature was higher than 650°C. It is believed that the gel precursor and hydrothermal environment play an important role in the formation of the nanowires at a low temperature. Owing to the better packing efficiency and therefore a good sinterability of the freestanding nanowhiskers, the pressed pellets made by NKBT nanowires showed >98% theoretical density at 1100°C for 2 h. The sol–gel–hydrothermal-derived ceramics have typical characteristics of relaxor ferroelectrics, and the piezoelectric properties were better than the ceramics prepared by the conventional sol–gel and solid-state reaction. 相似文献
12.
Shi Chen Mengjia Wu Liqiong An Yongxiang Li Shiwei Wang 《Journal of the American Ceramic Society》2007,90(2):664-666
Upconversion emission properties of Na1/2 Bi1/2 TiO3 :Er3+ ceramics prepared by the solid-state reaction method were analyzed as a function of Er3+ concentration and incident pump power. Strong green (550 nm) and red (670 nm) emission bands were observed with 980 nm excitation at room temperature. Experimental results showed that the emission bands can be tuned by changing Er3+ concentration. Upconversion processes in these samples result from not only a two-photon excited-state absorption process but also a nonradiative energy transfer and cross-relaxation process. 相似文献
13.
A type of new low sintering temperature ceramic, Li2 TiO3 ceramic, has been found. Although it is difficult for the Li2 TiO3 compound to be sintered compactly at temperatures above 1000°C for the volatilization of Li2 O, dense Li2 TiO3 ceramics were obtained by conventional solid-state reaction method at the sintering temperature of 900°C with the addition of ZnO–B2 O3 frit. The sintering behavior and microwave dielectric properties of Li2 TiO3 ceramics with less ZnO–B2 O3 frit (≤3.0 wt%) doping were investigated. The addition of ZnO–B2 O3 frit can lower the sintering temperature of the Li2 TiO3 ceramics, but it does not apparently degrade the microwave dielectric properties of the Li2 TiO3 ceramics. Typically, the good microwave dielectric properties of ɛr =23.06, Q × f =32 275 GHz, τf = 35.79 ppm/°C were obtained for 2.5 wt% ZnO–B2 O3 frit-doped Li2 TiO3 ceramics sintered at 900°C for 2 h. The porosity was 0.08%. The Li2 TiO3 ceramic system may be a promising candidate for low-temperature cofired ceramics applications. 相似文献
14.
Kyung-Hoon Cho Hwi-Yeol Park Cheol-Woo Ahn Sahn Nahm Kenji Uchino Seung-Ho Park Hyeung-Gyu Lee Hwack-Joo Lee 《Journal of the American Ceramic Society》2007,90(6):1946-1949
The 0.95(Na0.5 K0.5 )NbO3 –0.05SrTiO3 (0.95NKN–0.05ST) ceramics formed in this study had a porous microstructure with small grains and low piezoelectric properties due to their low density. However, when a small amount of Na2 O was intentionally subtracted from the 0.95NKN–0.05ST ceramics, a liquid phase was formed, which led to increased density and grain size. Piezoelectric properties were also improved for the Na2 O-subtracted 0.95NKN–0.05ST ceramics. The increased density and grain size were responsible for the enhancement of the piezoelectric properties. In particular, the 0.95(Na0.49 K0.5 )NbO2.995 –0.05ST ceramics showed high piezoelectric properties of d 33 =220, k p =0.4, Q m =72, and ɛ3 T /ɛo =1447, thereby demonstrating their promising potential as a candidate material for application to lead-free piezoelectric ceramics. 相似文献
15.
Jing-Feng Li Ke Wang Bo-Ping Zhang Li-Min Zhang 《Journal of the American Ceramic Society》2006,89(2):706-709
Lead-free piezoelectric ceramics have received attention because of increasing interest in environmental protection. Niobate ceramics such as NaNbO3 and KNbO3 have been studied as promising Pb-free piezoelectric ceramics, but their sintering densification is fairly difficult. In the present study, highly dense Na0.5 K0.5 NbO3 ceramics were prepared using spark plasma sintering (SPS). Although the SPS temperature was as low as 920°C, the density of the Na0.5 K0.5 NbO3 solid solution ceramics was raised to 4.47 g/cm3 (>99% of the theoretical density). After post-annealing in air, reasonably good ferroelectric and piezoelectric properties were obtained in the Na0.5 K0.5 NbO3 ceramics with submicron grains. The crystal phase of the Na0.5 K0.5 NbO3 has an orthorhombic structure. The Curie temperature is 395°C and the piezoelectric parameter ( d 33 ) of the Na0.5 K0.5 NbO3 ceramics reached 148 pC/N. 相似文献
16.
Hwi-Yeol Park Cheol-Woo Ahn Kyung-Hoon Cho Sahn Nahm Hyeung-Gyu Lee Hyung-Won Kang Duk-Hee Kim Kyeong-Soon Park 《Journal of the American Ceramic Society》2007,90(12):4066-4069
The sintering temperature of 0.95(Na0.5 K0.5 )NbO3 –0.05BaTiO3 (NKN–BT) ceramics needs to be decreased below 1000°C to prevent Na2 O evaporation, which can cause difficulties in poling and may eventually degrade their piezoelectric properties. NKN–BT ceramics containing CuO were well sintered at 950°C with grain growth. Poling was easy for all specimens. Densification and grain growth were explained by the formation of a liquid phase. The addition of CuO improved the piezoelectric properties by increasing the grain size and density. High piezoelectric properties of d 33 =230 pC/N, k p =37%, and ɛ3 T /ɛ0 =1150 were obtained from the specimen containing 1.0 mol% of CuO synthesized by the conventional solid-state method. 相似文献
17.
Sung Min Rhim Seokmin Hong Heungjin Bak Ok Kyung Kim 《Journal of the American Ceramic Society》2000,83(5):1145-1148
The effects of B2 O3 addition on the sintering behavior and the dielectric and ferroelectric properties of Ba0.7 Sr0.3 TiO3 (BST) ceramics were investigated. The dielectric and ferroelectric properties of a BST sample with 0.5 wt% B2 O3 sintered at <1150°C were as good as those of undoped BST sintered at 1350°C, and the dielectric loss was better. When >1.0 wt% B2 O3 was added to BST, the overdoped B2 O3 did not form a liquid phase or volatilize; it remained in the samples and formed a secondary phase that lowered the sintering behavior and the dielectric and ferroelectric properties of the BST. 相似文献
18.
Microstructure development in Bi0.5 (Na0.5 K0.5 )0.5 TiO3 prepared by a reactive-templated grain growth process was dependent on the sizes of platelike Bi4 Ti3 O12 (BiT) and equiaxed TiO2 particles used as starting materials. Calcined compacts were composed of large, platelike template grains and small, equiaxed matrix grains, the sizes of which were determined by those of the BiT and TiO2 particles, respectively. Texture was developed by the growth of template grains at the expense of matrix grains during sintering, and a new mechanism of grain growth was proposed on the basis of microstructure observation. The grain growth rate was determined by the template and matrix grain sizes, and a dense ceramic with extensive texture was obtained using small BiT and TiO2 particles. 相似文献
19.
Xueyi Sun Jinxia Deng Ce Sun Jichao Li Jun Chen Ranbo Yu Guirong Liu Xianran Xing Lijie Qiao 《Journal of the American Ceramic Society》2009,92(8):1853-1855
Lead-free potassium sodium niobate-based piezoelectric ceramics (1− y )(Na0.5−0.5 x K0.5−0.5 x Li x )NbO3 − y BiScO3 ( y =0.01, x= 0–0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y =0.01, abbreviated as KNNBSL100 x ). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02≤ x ≤0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3 . These solid solution ceramics are promising as potential lead-free candidate materials. 相似文献
20.
Hongliang Du Daijun Liu Fusheng Tang Dongmei Zhu Wancheng Zhou Shaobo Qu 《Journal of the American Ceramic Society》2007,90(9):2824-2829
Lead-free piezoelectric (K0.5 Na0.5 )NbO3 – x wt% Bi2 O3 ceramics have been synthesized by an ordinary sintering technique. The addition of Bi2 O3 increases the melting point of the system and improves the sintering temperature of (K0.5 Na0.5 )NbO3 ceramics. All samples show a pure perovskite phase with a typical orthorhombic symmetry when the Bi2 O3 content <0.7 wt%. The phase transition temperature of orthorhombic–tetragonal ( T O − T ) and tetragonal–cubic ( T C ) slightly decreased when a small amount of Bi2 O3 was added. The remnant polarization P r increased and the coercive field E c decreased with increasing addition of Bi2 O3 . The piezoelectric properties of (K0.5 Na0.5 )NbO3 ceramics increased when a small amount of Bi2 O3 was added. The optimum piezoelectric properties are d 33 =140 pC/N, k p =0.46, Q m =167, and T C =410°C for (K0.5 Na0.5 )NbO3 –0.5 wt% Bi2 O3 ceramics. 相似文献