共查询到20条相似文献,搜索用时 890 毫秒
1.
Dunmin Lin Kin Wing Kwok Huyong Tian Helen Wong Lai-wa Chan 《Journal of the American Ceramic Society》2007,90(5):1458-1462
Lead-free piezoelectric ceramics (Na1− x K x )(Nb1− y Sb y )O3 + z mol% MnO2 have been prepared by a conventional solid-state sintering technique. Our results reveal that Sb5+ diffuses into the K0.5 Na0.5 NbO3 lattices to form a solid solution with a single-phase orthorhombic perovskite structure. The partial substitution of Sb5+ for B-site ion Nb5+ decreases the paraelectric cubic-ferroelectric tetragonal phase transition ( T c ) and the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ( T O–F ), and retains strong ferroelectricity. A small amount of MnO2 is enough to improve the densification of the ceramics. The co-effects of MnO2 doping and Sb substitution lead to significant improvements in ferroelectric and piezoelectric properties. The ceramics with x =0.45–0.525, y =0.06–0.08, and z =0.5–1 exhibit excellent ferroelectric and piezoelectric properties: d 33 =163–204 pC/N, k P =0.47–0.51, k t =0.46–0.52, ɛ=640–1053, tan δ=1.3–3.0%, P r =18.1–22.6 μC/cm2 , E c =0.72–0.98 kV/mm, and T C =269°–314°C. 相似文献
2.
Jiangtao Zeng Yanghong Zhang Liaoying Zheng Gurong Li Qingrui Yin 《Journal of the American Ceramic Society》2009,92(3):752-754
(1− x )K0.5 Na0.5 NbO3 – x K3 Li2 Nb5 O15 (KNN–100 x KLN) ceramics were prepared by the solid-state reaction method. The results showed that small amount of KLN ( x ≤0.02) incorporated into the lattice and formed a single phase perovskite structure. The KLN modification lowered the phase transition temperature of orthorhombic–tetragonal ( T O−T ) and increased the Curie temperature ( T c ), but the transition temperatures remained almost unchanged in the range of x from 0.02 to 0.03. Small amount of KLN decreased the amount of defects, thus the remnant polarization increased and the coercive field decreased markedly, and the piezoelectric properties of KNN ceramics modified by small amount of KLN also enhanced markedly. 相似文献
3.
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
4.
Sergey Kucheiko Dong-Hun Yeo Ji-Won Choi Seok-Jin Yoon Hyun-Jai Kim 《Journal of the American Ceramic Society》2002,85(5):1327-1329
The microwave dielectric properties of CaTi1− x (Al1/2 Nb1/2 ) x O3 solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO3 . The substitution of Ti4+ by Al3+ /Nb5+ improved the quality factor Q of the sintered specimens. A small addition of Li3 NbO4 (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛr ) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τf ) of −2 ppm/K. Li3 NbO4 as a sintering additive had no harmful influence on τf of ceramics. 相似文献
5.
Jiagang Wu Ting Peng Yuanyu Wang Dingquan Xiao Jumu Zhu Yong Jin Jianguo Zhu Ping Yu Lang Wu Yihang Jiang 《Journal of the American Ceramic Society》2008,91(1):319-321
(1− x )(K0.48 Na0.52 )(Nb0.95 Ta0.05 )O3 – x LiSbO3 [(1− x )KNNT− x LS] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases was identified in the composition range of 0.03< x <0.05. The ceramics near the MPB exhibit a strong compositional dependence and enhanced electrical properties. The (1− x )KNNT– x LS ( x =0.04) ceramics exhibit good electrical properties ( d 33 =250 pC/N, k p =45.1%, k t =46.3%, T c =348°C, T o − t =74°C, P r =25.9 μC/cm2 , E c =10.7 kV/cm, ɛr ∼1352, tan δ∼3%). These results show that (1− x )KNNT– x LS ceramic is a promising lead-free piezoelectric material. 相似文献
6.
Dunmin Lin Kin Wing Kwok Helen Wong Lai-wa Chan 《Journal of the American Ceramic Society》2009,92(6):1362-1365
In this work, the double-loop-like characteristics of K0.5 Na0.5 NbO3 + x mol% K5.4 Cu1.3 Ta10 O9 ceramic and its relationships with the transition temperature, aging, and switching have been investigated. Our results reveal that the phase transition temperature is an important parameter determining the aging requirement for the ceramics to exhibit the double-loop-like characteristics. For a ceramic with a high transition temperature, e.g. the ceramic with x =0.75 (tetragonal–orthorhombic phase temperature ∼206°C), the vacancies can migrate during the crystal transformation and settle in a distribution with the same symmetry as the crystal after the transformation. As a result, defect dipoles along the polarization direction are formed and provide restoring forces to reverse the switched polarizations, and thus producing a double polarization hysteresis ( P – E ) loop. On the other hand, aging is required for a ceramic with a low transition temperature, e.g. aging at 80°C for 30 days is required for the ceramic with x =1.5 (transition temperature ∼175°C). Our results also reveal that the defect dipoles can be switched under a slow-switching electric field (<1 Hz) or at high temperatures (>100°C), thus leading to an opening of the double P – E loop. 相似文献
7.
K2 O activity in K+ -(α+β)-alumina was determined from emf data of the galvanic cell Pt,O2 ,(α+β)-alumina/K+ -β-alumina/K2 SO4 ,SO2 +SO3 +O2 ,Pt. K2 O activity in the K+ -(α+β)-alumina was expressed by the equation log ak2o (±0.038)=(−18295±120)(K/T)+(0.998±0.110), where 961 K+ -β-alumina are discussed: the standard Gibbs energy of formation of K2 O·11Al2 O3 from K2 O and α-Al2 O3 and from K, O, and Al; the thermodynamic stabilities of K+ -β-alumina in the atmospheres of SOx (x=2, 3) and CO2 ; the equilibrium vapor pressure of potassium over K+ -β-alumina under a constant O2 pressure; and the stability of K+ -β-alumina in the molten Na-K alloy. 相似文献
8.
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
9.
Jiagang Wu Dingquan Xiao Yuanyu Wang Lang Wu Yihang Jiang Jianguo Zhu 《Journal of the American Ceramic Society》2008,91(7):2385-2387
[(K x Na1 − x )0.95 Li0.05 ](Nb0.95 Ta0.05 )O3 (K x NLNT) ( x= 0.40–0.60) lead-free piezoelectric ceramics were prepared by conventional solid-state sintering. The effects of K/Na ratio on the dielectric, piezoelectric, and ferroelectric properties of the K x NLNT ceramics were studied. The experimental results show that the electrical properties strongly depend on the K/Na ratio in the K x NLNT ceramics. The K x NLNT ( x =0.42) ceramics exhibit enhanced properties ( d 33 ∼242 pC/N, k p ∼45.7%, k t ∼47%, T c ∼432°C, T o−t =48°C, ɛr ∼1040, tanδ∼2.0%, P r ∼26.4 μC/cm2 , E c ∼10.3 kV/cm). Enhanced electrical properties of the K x NLNT ( x =0.42) ceramics could be attributed to the polymorphic phase transition near room temperature. These results show that the K x NLNT ( x =0.42) ceramic is a promising lead-free piezoelectric material. 相似文献
10.
Yuanyu Wang Qibin Liu Jiagang Wu Dingquan Xiao Jianguo Zhu 《Journal of the American Ceramic Society》2009,92(3):755-757
(1− x )(Na0.5 K0.5 )NbO3 – x AgSbO3 lead-free piezoelectric ceramics were prepared by normal sintering. The effects of the AgSbO3 on the phase structure and piezoelectric properties of the ceramics were systematically studied. These results show that the AgSbO3 -modified (K0.50 Na0.50 )NbO3 lead-free piezoelectric ceramics form stable solution with orthorhombic structure, and the Curie temperature and the polymorphic phase transition of the ceramics decreased with increasing AgSbO3 . The result shows that the piezoelectric properties of the ceramics strongly depend on the AgSbO3 . The ceramics with x =0.05 possess optimum properties ( d 33 =192 pC/N, k p =43%, T c =348°C, T o−t =145°C, ɛr ∼632, and tan δ∼3.5%). These results indicate that the ceramic is a promising candidate material for lead-free piezoelectric ceramics. 相似文献
11.
Phase relations in the system were studied between 600° and 350°C. All three end members have the pyroxene-type structure. Both LiVO3 and NaVO3 are monoclinic, whereas KVO3 takes the orthorhombic symmetry. At 360°C, the join LiVO3 –NaVO3 is characterized by two series of pyroxene-type solid solutions: NaVO3 –(Na0.44 Li0.56 )VO3 and LiVO3 -(Na0.16 Li0.84 )-VO3 . (K0.5 Na0.5 )VO3 and (K0.5 Li0.5 )VO3 are two other stable phases at 360°C. The pyroxene-type (K0.5 Na0.5 )VO3 has a range of solid solution from (K0.6 Na0.4 )VO3 to (K0.4 Na0.6 )VO3 along the join and extends into the ternary field with a maximum of 13 mol% LiVO3 . (K0.5 Li0.5 )VO3 has no detectable range of solid solution, and its X-ray powder diffraction data cannot be indexed based upon either the monoclinic or the orthorhombic unit cell. 相似文献
12.
SHIGERU ITO NOBUO KUBO SHINYA NARIKI NOBORU YONEDA 《Journal of the American Ceramic Society》1987,70(12):874-879
The potassium ions in potassium β-ferrite ((1 + x)K2 O ·11Fe2 O3 ) crystals were exchanged with Na+ , Rb+ , Cs+ , Ag+ , NH4 + , and H3 O+ in molten nitrates or in concentrated H2 SO4 . On the other hand, spinel and hexagonal ferrites were formed by soaking the crystals in the melt of divalent salts. The crystals of K+ , Rb+ , and Cs+ β-ferrites decomposed to form α-Fe2 O3 at high temperatures of 800° to 1100°C. In addition, H3 O+ , NH4 + , and Ag+ β-ferrites decomposed to form α-Fe2 O3 at relatively low temperatures of 350° to 650°C, in accordance with the stabilities of the inserted ions. The electrical properties of some β-ferrites were measured. 相似文献
13.
Shinichi Kikkawa Namie Kato Noriko Taya Masakazu Tada Fumikazu Kanamaru 《Journal of the American Ceramic Society》1995,78(5):1387-1390
Both NaCuO2 -type Ca0.85 CuO2 and infinite-layered (Ca1- x Sr x )CuO2 could be prepared much more easily by firing the dried solids from mixed acetate aqueous solutions titrated with tartaric acid than by normal calcination. The presence of a narrow solid-solution composition range of 0.10 < x > 0.16 was confirmed in infinite-layered (Ca1- x Sr x )CuO2 in the preparation using the tartrate route. The calcium could also be substituted by sodium in a range of y > 0.15 in NaCuO2 -type (Ca1- y Na y )0.85 CuO2 using the same route. Further substitution of Ca2+ with Y3+ might also be possible in infinite-layered (Ca1- x Sr x )CuO2 , but resulted in the NaCuO2-type compound in the substitution with Na+ . 相似文献
14.
Sodium-rich NASOCON-type ceramics, the NaM2 (PO4 )3 +y Na2 O (M = Ge, Ti, Hf, Zr) system, were investigated in order to obtain a material having a high Na+ conductivity and high density. The ionic conductivity and the sinterability were greately improved by an increase in the valve of y for all of the system examined. Added Na2 O was not souble in teh NASICON-type skeletton, sice the lattice constants and teh X-ray diffraction patterns were not changed by the Na2 O addintion in all of the samples. Na2 O acts as a flux for obtaining highly dense ceramics and highly conductive grain boundaries. Partial A2 site insertion by Na+ ions is effective for the enhancement of conductivity, because the conductivity for Na1.5 M(III)0.5 Zr1.5 (PO4 )3 (M = In or Y) is about 1 order of magnitude higher than the maximum conductivity of the NaZr2 (PO4 )3 +y Na2 O system. 相似文献
15.
Lead-free (K0.44 Na0.52 Li0.04 ) (Nb0.96−x Tax Sb0.04 )O3 piezoelectric ceramics were prepared by the conventional solid-state sintering method. The grain growth of the ceramics was inhibited and the relative density was improved with Ta substituting for Nb. Increasing x led to different variations of dielectric properties before and after poling, and prevented the occurrence of orthorhombic–tetragonal phase transition (at T o − t ). All the ceramics show an intermediate relaxor-like behavior between normal and ideal relaxor ferroelectrics. Significantly enhanced dielectric and piezoelectric properties were obtained in the ceramics with x =0.20. The ceramics are very promising lead-free materials for electromechanical device applications. 相似文献
16.
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
17.
Harumi Yokokawa Tatsuya Kawada Masayuki Dokiya 《Journal of the American Ceramic Society》1989,72(1):152-153
It has been found that the enthalpy of formation of perovskite compounds, Δf H° (ABO3 , B = transition metais), from binary oxides can be well characterized in terms the tolerance factor, t≡(rA + ro )√2 (rB + ro ), where rA and rB are the radii of A-site ions with 12-coordination and B-site ions with 6-coordination, respectively, and Δf H°=−168 + 270(1 − t) kJ·mol−1 for AI BV O3 , Δf H°=−125 + 1000(1 − t) kJ·mol−1 for AII BIV O3 , and Δf H°=− 90 + 720(1 − t) kJ·mol−1 for AIII BIII O3 . Although the thermodynamic data of K2 NiF4 compounds are not extensive, a similar regularity can be found when use is made of the radii of A-site ions with 9-coordination for the K2 NiF4 compounds. These correlations will be quite useful in predicting. 相似文献
18.
Yuanyu Wang Jiagang Wu Dingquan Xiao Wenjuan Wu Bing Zhang Lang Wu Jianguo Zhu 《Journal of the American Ceramic Society》2008,91(8):2772-2775
[(K0.50 Na0.50 )0.95− x Li0.05 Ag x ](Nb0.95 Ta0.05 )O3 (KNLNANT- x ) lead-free piezoelectric ceramics were prepared by normal sintering. Effects of the Ag content on the microstructure and electrical properties of KNLNANT- x ceramics were systematically investigated. It is found that the ceramics with x =0.03 exhibit relatively good electrical properties along with high Curie temperature: ( d 33 ∼252 pC/N, T c ∼438°C, k p ∼45.4%, P r ∼30.1 μC/cm2 , E c ∼13.8 kV/cm, ɛr ∼1030, and tan δ∼2.6%). The related mechanism for enhanced electrical properties of the ceramics was also discussed. These results show that KNLNANT-0.03 ceramic is a promising candidate material for high temperature lead-free piezoelectric ceramics. 相似文献
19.
Qiyi Yin Shuoguo Yuan Qiang Dong Changan Tian 《Journal of the American Ceramic Society》2010,93(1):167-170
A new type (1− x )(K0.485 Na0.485 Li0.03 )NbO3 – x Pb(Zr0.53 Ti0.47 )O3 piezoelectric ceramics was fabricated by conventional ceramics sintering technique. Their microstructure and electrical properties of the ceramics were also studied. X-ray diffraction and scanning electron microscopy patterns indicate that all ceramics samples exhibit a pure perovskite and highly dense structure, and the coexistence of the tetragonal and orthorhombic phases is formed; The ceramic with x =0.75 exhibits the following excellent properties: d 33 =363 pC/N, k p =63%, Q m =142, ɛr =1590, tan δ=1.70%, P r =28.6 μC/cm2 , E c =0.89 kV/mm, T c =295°C. These results indicate that the ceramic is a promising candidate for piezoelectric ceramics in practical applications. 相似文献
20.
C. C. Khaw C. K. Lee Z. Zainal G. C. Miles A. R. West 《Journal of the American Ceramic Society》2007,90(9):2900-2904
The subsolidus phase diagram of the system Bi2 O3 –ZnO–Ta2 O5 in the region of the cubic pyrochlore phase has been determined at 1050°C. This phase forms a solid solution area that includes the ideal composition P, Bi3 Zn2 Ta3 O14 ; possible solid solution mechanisms are proposed, supported by density measurements of Zn-deficient solid solutions. The general formula of the solid solutions is Bi3+ y Zn2− x Ta3− y O14− x − y , based on the creation of Zn2+ , O2− vacancies in Zn-deficient compositions and a variable Bi/Ta ratio. 相似文献