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1.
Yun Hou Min Wang Xiao-Hong Xu Dong Wang Hong Wang Shu-Xia Shang 《Journal of the American Ceramic Society》2002,85(12):3087-3089
Nanopowders of Bi2 Ti2 O7 were synthesized by a metallorganic decomposition (MOD) technique. Pure Bi2 Ti2 O7 nanocrystals formed after annealing at 550°C for 5 min. X-ray patterns show that Bi20 TiO32 is a metastable phase during Bi2 Ti2 O7 formation. It was found that there were two peaks in the curves of the dielectric response as a function of temperature for pressed nanocrystalline Bi2 Ti2 O7 samples. The Curie temperature decreases with decrease of grain size whereas the ferroelectric-ferroelectric phase transition temperature increases. The hysteresis loops observed also suggest that Bi2 Ti2 O7 might belong to a ferroelectric material. 相似文献
2.
TOSHIO KIMURA TAKANOBU KANAZAWA TAKASHI YAMAGUCHI 《Journal of the American Ceramic Society》1983,66(8):597-600
The reaction between Bi2 O3 and TiO2 in molten LiCl-KCl was examined with special emphasis on the reaction mechanism and the size of Bi4 Ti3 O12 particles. The oxides reacted with LiCl to form an intermediate compound, which changed into Bi4 Ti3 O12 on extended heating. Potassium chloride retarded the reaction between the oxides and LiCl and promoted the change from the intermediate compound to Bi4 Ti3 O12 . Bi4 Ti3 O12 particles prepared in the flux were platelike, irrespective of the preparation conditions, but their size depended on reaction temperature and time, the ratio of LiCl to KCl, and the amount of flux. 相似文献
3.
The system TiO2 -Bi2 Ti4 O11 was examined by Raman spectroscopy and X-ray diffraction to determine whether TiO2 is soluble in Bi2 Ti4 O11 . The Raman spectral data obtained from preparations made at ∼ 1050°C and cooled to room temperature led us to conclude that TiO2 is not soluble in the "high-temperature" form of Bi2 Ti4 O11 . It was also found that extensive grinding of the phase identified as the "high-temperature" form converts it to the "low-temperature" form, stable below 250°C. 相似文献
4.
Xingsen Gao Zhaohui Zhou Junmin Xue John Wang 《Journal of the American Ceramic Society》2005,88(4):1037-1040
Effects of excess Bi2 O3 content on formation of (Bi3.15 Nd0.85 )Ti3 O12 (BNT) films deposited by RF sputtering were investigated. The microstructures and electrical properties of BNT thin films are strongly dependent on the excess Bi2 O3 content and post-sputtering annealing temperature, as examined by XRD, SEM, and P – E hysteresis loops. A small amount of excess bismuth improves the crystallinity and therefore polarization of BNT films, while too much excess bismuth leads to a reduction in polarization and an increase in coercive field. P – E loops of well-established squareness were observed for the BNT films derived from a moderate amount of Bi2 O3 excess (5 mol%), where a remanent polarization 2P r of 25.2 μC/cm2 and 2E c of 161.5 kV/cm were shown. A similar change in dielectric constant with increasing excess Bi2 O3 content was also observed, with the highest dielectric constant of 304.1 being measured for the BNT film derived from 5 mol% excess Bi2 O3 . 相似文献
5.
Hong-Wen Wang 《Journal of the American Ceramic Society》1995,78(4):1134-1135
in a recent article of the Journal , Yu et al .1 reported their experimental results on the effect of Al2 O3 and Bi2 O3 on the formation mechanism of Sn-doped Ba2 Ti9 O20 . They claimed that both Al2 O3 and Bi2 O3 can dramatically assist the formation of Sn-doped Ba2 Ti9 O20 but are based on different mechanisms. They concluded that first, Bi2 O3 melts above 830°C and accelerates the migration of the involved reactants to form Ba2 Ti9 O20 ; second, Al2 O3 can reduce the height of the potential energy barrier of the formation of Ba2 Ti9 O20 due to the intergrowth of BaAl2 Ti6 O16 phase. They explained their results from a point of view that the formation of Ba2 Ti9 O20 is controlled by (1) the migration of reactants to the interfaces and (2) the height of the potential-energy barrier of the reaction at the interfaces. However, based on their results, we feel their conclusions are incautious and may be misleading, as will be discussed later. 相似文献
6.
Ferroelectric thin films of bismuth-containing layered perovskite Bi4 Ti3 O12 have been fabricated by a metalorganic decomposition (MOD) method. Crack-free and crystalline films of ∼5000 Å thickness have been deposited on Pt/Ti/SiO2 /Si substrates. Different heat treatments have been studied to investigate the nucleation and growth of perovskite Bi4 Ti3 O12 crystallites. If the same composition and final annealing temperature are used, films with different orientations are obtained by different heating schedules. These films show a large anisotropy in ferroelectric properties. Theoretical considerations are presented to suggest that nucleation control is responsible for texture and grain-size evolution. Moreover, the origin of the ferroelectric anisotropy is rooted in the two-dimensional nature of layered polarization. 相似文献
7.
Darko Makovec Irena Priboic Zoran Samardija Miha Drofenik 《Journal of the American Ceramic Society》2001,84(11):2702-2704
The solid solubility of the aliovalent dopants Fe3+ and Nb5+ in the BaBi4 Ti4 O15 compound, a member of the family of Aurivillius bismuth-based layer-structure perovskites, has been studied using quantitative wavelength-dispersive spectroscopic microanalysis (SEM/EPMA) in combination with X-ray powder diffractometry (XRPD). The samples with nominal (starting) compositions corresponding to the chemical formulas BaBi4 Ti4–4 X Fe4 X O15 and BaBi4 Ti4–4 X Nb4 X O15 were prepared by hot forging a mixture of BaTiO3 and Bi4 Ti3 O12 with additions of Fe2 O3 or Nb2 O5 followed by a long annealing at 1100°C. The study showed that an excess charge introduced into the structure by the substitution of Ti4+ ions with aliovalent dopants was preferentially compensated by a change in the ratio of Ba2+ to Bi3+ ions in the host structure according to the general formulas of the solid solutions Ba1–4 X Bi4+4 X Ti4–4 X Fe' 4 X O15 and Ba1+4 X Bi4–4 X Ti4–4 X Nb· 4 X O15 . 相似文献
8.
Yunyi Wu Duanming Zhang Jun Yu Yunbo Wang 《Journal of the American Ceramic Society》2009,92(2):501-505
Praseodymium doped Bi4 Ti3 O12 (BTO) thin films with composition Bi3.63 Pr0.3 Ti3 O12 (BPT) were successfully prepared on Pt/Ti/SiO2 /Si substrates by RF-magnetron sputtering method at substrate temperatures ranging between 500° and 750°C. The structural phase and orientation of the deposited films were investigated in order to understand the effect of the deposition temperature on the properties of the BPT films. As the substrate temperature was increased to 700°C, the films started showing a tendency of assuming a c -axis preferred orientation. At lower temperatures, however, polycrystalline films were formed. The Pt/BPT/Pt capacitor showed an interesting dependence of the remnant polarization (2 P r ) as well as dc leakage current values on the growth temperature. The film deposited at 650°C showed the largest 2 P r of 29.6 μC/cm2 . With the increase of deposited temperature, the leakage current densities of films decreased at the same applied field and the film deposited at 750°C exhibited the best leakage current characteristics. In addition, the ferroelectric fatigue and Raman measurements were carried out on the as-prepared, postannealed in air and postannealed in oxygen BPT films. It was revealed that the BPT film postannealed in air exhibited the weakest fatigue-resistance characteristics and highest frequency shifted Raman vibration modes, indicating the highest oxygen vacancy concentration in this film. 相似文献
9.
Jiaqing Yu Hangwei Zhao Jiasheng Wang Fei Xia 《Journal of the American Ceramic Society》1994,77(4):1052-1056
High-performance Ba2 Ti9 O20 ceramics are attracting great attention, but their formation mechanism still is somewhat unclear. The present investigation shows that the formation of Ba2 Ti9 O20 can be promoted strikingly by the participation of Bi2 O3 and Al2 O3 . The effect of Bi2 O3 on the formation of Ba2 Ti9 O20 is attributed to the fact that migration of the involved reactants is accelerated by liquid which forms from the melting of Bi2 O3 above 830°C. This migration, however, is not the only rate-limiting factor. A high potential-energy barrier, resulting from stress that arises along the crystal-structured layers, also heavily restricts the formation of Ba2 Ti9 O20 . The participation of Al2 O3 , on the other hand, can reduce the height of this potential-energy barrier and effectively improve the kinetics of the formation of Ba2 Ti9 O20 by causing the formation of BaAI2 Ti6 O16 crystals; these crystals intergrow with Ba2 Ti9 O20 crystals and result in decreased stress. 相似文献
10.
Qing-Yuan Tang Yan-Mei Kan Pei-Ling Wang Yao-Gang Li Guo-Jun Zhang 《Journal of the American Ceramic Society》2007,90(10):3353-3356
Powders of Nd/V-doped Bi4 Ti3 O12 with a composition Bi3.74 Nd0.26 Ti2.98 V0.02 O12.01 (BNTV), prepared by the molten salt synthesis, using chlorides as the fluxes, were successfully obtained. The influences of the molar ratio of KCl to NaCl, temperature, and soak time on the formation and morphology of BNTV were investigated. The results indicated that Na+ can enter the lattice of Bi4 Ti3 O12 (BIT), leading to a decrease in the cell dimensions of BIT phase. The grain size and morphology of BNTV powders were considerably affected by the molar ratio of KCl to NaCl in the fluxes, in which the platelets showed the morphology of a rectangle and no regular shape in KCl and NaCl fluxes, respectively. The grain size of BNTV increased with increasing amount of NaCl in the fluxes, but the thickness decreased. The platelets prepared in the NaCl flux were faceted along (0 0 1) plane. 相似文献
11.
Extended defects in ZnO ceramics containing, 6 wt% Bi4 Ti3 O12 were studied by analytical electron microscopy. Apart from basal plane condensation stacking faults, which are also present in as-received ZnO, extended defects related to the presence of Bi4 Ti3 O12 were observed. In samples sintered at 900°C they lie in the basal or in the prismatic planes and they quite often form closed loops, whereas they form serpentine-shaped boundaries in samples sintered at 1200°C. Evidence is given that they are inversion boundaries. Their TEM image characteristics, as well as the unambiguous presence of Ti at the boundaries, suggest that they are formed due to the presence of 2-D coherent precipitates of Ti-rich (possibly Zn2 TiO4 -type spinel) phase. 相似文献
12.
Maria V. Gelfuso Daniel Thomazini José A. Eiras 《Journal of the American Ceramic Society》1999,82(9):2368-2372
SrBi4 Ti4 O15 ceramics were prepared via ordinary firing (OF) and hot forging (HF). Characterization using scanning electron microscopy and X-ray diffractometry shows platelike grains that were highly oriented ( F = 0.95) after hot forging. Ferroelectric, dielectric, and piezoelectric characterizations revealed that polarization reorientation was restricted to the ab plane of the orthorhombic structure, parallel to the (Bi2 O2 )2+ layers. The thickness coupling factor for OF samples was only half that for HF samples oriented parallel to the HF direction (in the ab-plane), as a consequence of poling restrictions in randomly oriented grains. 相似文献
13.
Ju Hong Miao Tsang-Tse Fang Han-Yang Chung Chao-Wei Yang 《Journal of the American Ceramic Society》2009,92(11):2762-2764
Undoped and La-doped Bi2 Fe4 O9 ceramics were synthesized using a soft chemical method. It is observed that in calcining La-doped Bi2 Fe4 O9 , Bi(La)FeO3 phase rather than Bi2− x La x Fe4 O9 gradually increases with increasing La doping content. The phase conversion from mullite-type structure of Bi2 Fe4 O9 to rhombohedrally distorted perovskite one of Bi(La)FeO3 with increasing La doping content indicates that La doping can stabilize the structure of BiFeO3 . This is further evidenced that Bi2 Fe4 O9 can be directly converted to Bi(La)FeO3 by heating the mixtures of nominal composition of Bi2 Fe4 O9 / x La2 O3 . Furthermore, the microstructure changes and the room temperature hysteresis loops and leakage current for Bi2− x La x Fe4 O9 with x =0 and 0.02 were characterized. 相似文献
14.
M. Algueró P. Ferrer E. Vila J. E. Iglesias A. Castro 《Journal of the American Ceramic Society》2006,89(11):3340-3347
The processing of ferroelectric Bi4 Ti3 O12 ceramics from powders prepared by wet no-coprecipitation chemistry (WNCC) and mechanochemical activation (MCA) has been investigated. Dense ceramics were obtained at sintering temperatures as low as 900°C. Exaggerated grain growth was observed for samples from WNCC, but not for those from MCA. Dielectric properties are discussed in relation to the type and concentration of defects, which is smaller for ceramic samples from WNCC. The activation energy of the dielectric relaxation for ceramics from MCA suggests that additional V O •• are present at the pseudoperovskite [Bi2 Ti3 O10 ]2− block in this case. 相似文献
15.
Hua Hao Han-xing Liu Yang Liu Ming-he Cao Shi-xi Ouyang 《Journal of the American Ceramic Society》2007,90(5):1659-1662
In this paper, the microwave-assisted molten salt method (MAMSS) and molten salt method (MSS) were used to synthesize SrBi4 Ti4 O15 (SBT). The phase constitution was determined by powder X-ray diffraction and the microstructure of powder was examined by scanning electron microscopy. In contrast to the conventional MSS method, MAMSS produces more distinct plate-like grains and synthesizes both SBT and Bi4 Ti3 O12 (BTO) at 600°C with a 30-min soaking time. The increase of temperature and soaking time can make the plate-like grains of BTO more distinct. 相似文献
16.
TAKESHI KIKUCHT 《Journal of the American Ceramic Society》1977,60(3-4):148-150
The subsolidus phase equilibria in the system Bi2 O3 -TiO2 -Nb2 O5 at 1100°C were determined by solid-state reaction techniques and X-ray powder diffraction methods. The system was found to contain 4 ternary compounds, i.e. Bi3 TiNbO9 , Bi7 Ti4 NbO21 , a cubic pyrochlore solid solution having a compositional range of 3Bi2 O3 · x TiO2 (7– x )Nb2 O5 where x ranges from 2.3 to 6.75, and an unidentified phase, 4Bi2 O3 ·11TiO2 ·5Nb2 O5 . 相似文献
17.
Marina Villegas Amador C. Caballero Carlos Moure Pedro Durán José F. Fernández 《Journal of the American Ceramic Society》1999,82(9):2411-2416
High-temperature piezoelectric ceramics based on W6+ -doped Bi4 Ti3 O12 (W-BIT) were prepared by both the conventional mixing oxides and the chemical coprecipitation methods. Sintering was carried out between 800° and 1150°C in air. A rapid densification, >99% of the theoretical density (rhoth ) at 900°C/2 h, took place in the chemically prepared W6+ -doped Bi4 Ti3 O12 ceramics, whereas conventionally prepared BIT-based materials achieved a lower maximum density, ∼94% of rhoth , at higher temperature (1050°C). The microstructure study revealed a platelike morphology in both materials. Platelike grains were larger in the conventionally prepared W-BIT-based materials. The sintering behavior could be related both to the agglomeration state of the calcined powders and to the enlargement of the platelets at high temperature. The W6+ -doped BIT materials showed an electrical conductivity value 2-3 orders of magnitude lower than undoped samples. The electrical conductivity increased exponentially with the aspect ratio of the platelike grains. The addition of excess TiO2 produced a further decrease of the electrical conductivity. 相似文献
18.
The dielectric characteristics of BaBi2 Nb2 O9 , BaBi4 Ti4 O15 , BaBi8 Ti7 O27 , and La-substituted SrBi4 Ti4 O4 were investigated to discuss their ferroelectric phase transition and relaxor behaviors. BaBi2 Nb2 O9 showed typical relaxor behaviors, and a shift of T m with increasing frequency was observed in BaBi4 Ti4 O15 and SrBi4− x La x Ti4 O15 ( x =0.8, 1.0) but they underwent a real paraelectric–ferroelectric phase transition on zero-field cooling, while BaBi8 Ti7 O27 showed a normal ferroelectric nature. The reduced concentration and weakened coupling of the dipoles related to A-site bismuth are believed to be responsible for the appearance of short-range electric ordering and the relaxor behaviors in these bismuth layer-structured compounds. 相似文献
19.
Shara S. Shoup ‡ Carlos E. Bamberger § Richard G. Haire 《Journal of the American Ceramic Society》1996,79(6):1489-1493
The compounds SrPu2 Ti4 O12 , Pu2 Ti3 O8.79 , and Pu2 Ti2 O7 , where plutonium is in the (III) oxidation state, were prepared and identified via X-ray diffraction (XRD). The solid solubility limit of Pu2 Ti2 O7 in Ln2 Ti2 O7 (Ln = Gd, Er, or Lu) was also studied via XRD; it was determined that the solubility of Pu2 Ti2 O7 increased as the radius of the lanthanide ion in the host compound decreased. Attempts to synthesize Sr2 Pu2 Ti5 O16 and Sr2 Ce2–y Puy Ti5 O16 solid solutions, where plutonium is in the (IV) oxidation state, were unsuccessful. 相似文献
20.
Ferroelectric thin films of bismuth-containing layered perovskite PbBi2 Nb2 O9 have been prepared by a metalorganic decomposition (MOD) method. Random and highly c-oriented films of the same starting composition have been obtained under different intermediate- and high-temperature heat treatments. A comparison of their crystallization and properties with those of Bi4 Ti3 O12 films reveals similar trends that are common to bismuth-containing Aurivillius compounds. Heterogeneous nucleation of the perovskite phase either on the pyrochlore (444) plane because of lattice matching or on the substrate surface because of lower interfacial energy is proposed as the cause of orientation selection during crystallization. The different thickness of the pseudoperovskite subunits in these layered compounds may be responsible for the systematic difference in the anisotropic ferroelectric properties. Smaller polarization and higher coercive field are expected for PbBi2 Nb2 O9 , which has thinner pseudoperovskite units than Bi4 Ti3 O12 . 相似文献