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1.
(1− x )(Na0.5K0.5)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 (K0.50Na0.50)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   

2.
Mn-doped 0.98K0.5Na0.5NbO3–0.02BiScO3 (0.98KNN–0.02BS) lead-free piezoelectric ceramics have been prepared by a conventional sintering technique and the effects of Mn doping on the phase structure and piezoelectric properties of the ceramics have been studied. Our results reveal that a small amount of Mn can improve the densification of the ceramics effectively. Because of the high densification, fine grain, and Mn doping effects, the piezoelectric and dielectric properties of the ceramics are improved considerably. Very good piezoelectric and dielectric properties of d 33=288 pC/N, k p=0.46, ɛr=1591, and T C=328°C were obtained for the 0.98KNN–0.02BS ceramics doped with 0.8 mol% Mn. Therefore, the 0.98KNN–0.02BS ceramics containing a small amount of Mn are a good candidate material for lead-free piezoelectric ceramics.  相似文献   

3.
(1− x )(Na0.5K0.5)NbO3– x LiNbO3 [(1− x )NKN– x LN] ceramics were produced by the conventional solid-state sintering method, and their microstructure and piezoelectric properties were investigated. The formation of the liquid phase and K6Li4Nb10O30 second phase that were observed in the (1− x )NKN– x LN ceramics was explained by the evaporation of Na2O during the sintering. A morphotropic phase boundary (MPB) was observed in the specimens with 0.05< x <0.08. Promising piezoelectric properties were obtained for the specimens with x =0.07. Therefore, the piezoelectric properties of this 0.93NKN–0.07LN ceramic were further investigated and were found to be influenced by their relative density and grain size. In particular, grain size considerably affected the d 33 value. Two-step sintering was conducted at different temperatures to increase the grain size. Piezoelectric properties of d 33=240 (pC/N) and k p=0.35 were obtained for the 0.93NKN–0.07LN ceramics sintered at 1030°C and subsequently annealed at 1050°C.  相似文献   

4.
(1− x )(Na0.5K0.5)NbO3–(Bi0.5K0.5)TiO3 solid solution ceramics were successfully fabricated, exhibiting a continuous phase transition with changing x at room temperature from orthorhombic, to tetragonal, to cubic, and finally to tetragonal symmetries. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal ferroelectric phases was found at 2–3 mol% (Bi0.5K0.5)TiO3 (BKT), which brings about enhanced piezoelectric and electromechanical properties of piezoelectric constant d 33=192 pC/N and planar electromechanical coupling coefficient k p=45%. The MPB composition has a Curie temperature of 370°–380°C, comparable with that of the widely used PZT materials. These results demonstrate that this system is a promising lead-free piezoelectric candidate material.  相似文献   

5.
A new type (1− x )(K0.485Na0.485Li0.03)NbO3– x Pb(Zr0.53Ti0.47)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   

6.
Lead-free potassium sodium niobate-based piezoelectric ceramics (1− x )(Na0.5K0.5)NbO3– x BiScO3 (KNN–BS) ( x =0∼0.05) have been prepared by an ordinary sintering process. Single perovskite phase of KNN–BS exhibits an orthorhombic symmetry at x <0.015 and pseudocubic symmetry at x >0.02, separating by a MPB at 0.015≤ x ≤0.02. Piezoelectric and ferroelectric properties are significantly enhanced in the MPB, which are as follows: piezoelectric constant d 33=203 pC/N, planar coupling coefficient k p=0.36, remnant polarization P r=24.4 μC/cm2. These solid solution ceramics look promising as a potential lead-free candidate materials.  相似文献   

7.
The 0.95(Na0.5K0.5)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 Na2O 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 Na2O-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(Na0.49K0.5)NbO2.995–0.05ST ceramics showed high piezoelectric properties of d 33=220, k p=0.4, Q m=72, and ɛ3To=1447, thereby demonstrating their promising potential as a candidate material for application to lead-free piezoelectric ceramics.  相似文献   

8.
The sintering temperature of 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (NKN–BT) ceramics needs to be decreased below 1000°C to prevent Na2O 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 ɛ3T0=1150 were obtained from the specimen containing 1.0 mol% of CuO synthesized by the conventional solid-state method.  相似文献   

9.
The microstructural development of crystalline-oriented (K0.5Na0.5)NbO3 (KNN)-based piezoelectric ceramics during sintering was investigated. The addition of CuO as a sintering aid was found to be effective for fabricating highly oriented and dense KNN ceramics. KNN specimens containing 0.5–1.0 mol% CuO sintered at 1100°C for 1 h were found to have relative densities and pseudo-cubic {100} orientation degrees of 95% or higher. In the early stages of sintering, KNN is formed in the reaction between complementary reactants NaNbO3 and KNbO3, after which oriented grain growth proceeds at a relative density of more than 90%. In addition, the results of transmission electron microscopy observation showed that textured KNN ceramics have a unique pectinate-like domain structure with domain walls consisting of {101} planes.  相似文献   

10.
(1− x )(K0.48Na0.52)(Nb0.95Ta0.05)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   

11.
[(K x Na1− x )0.95Li0.05](Nb0.95Ta0.05)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   

12.
The objective of this work was to lower the sintering temperature of K0.5Na0.5NbO3 (KNN) without reducing its piezoelectric properties. The KNN was sintered using 0.5, 1, 2, and 4 mass% of (K, Na)-germanate. The influence of the novel sintering aid, based on alkaline germanate with a melting point near 700°C, on the sintering, density, and piezoelectric properties of KNN is presented. The alkaline-germanate-modified KNN ceramics reach up to 96% of theoretical density at sintering temperatures as low as 1000°C, which is approximately 100°C less than the sintering temperature of pure KNN. The relative dielectric permittivity (ɛ/ɛ0) and losses (tanδ), measured at 10 kHz, the piezo d 33 coefficient, the electromechanical coupling and mechanical quality factors ( k p, k t, Q m) of KNN modified with 1 mass% of alkaline germanate are 397, 0.02, 120 pC/N, 0.40, 0.44, and 77, respectively. These values are comparable to the best values obtained for KNN ceramics sintered above 1100°C.  相似文献   

13.
Dolomite-type borate ceramics consisting of CaZrB2O6 were synthesized via a conventional solid-state reaction route; low-temperature sintering was explored using Bi2O3–CuO additives of 1–7 wt% for low-temperature co-fired ceramics applications. For several sintering temperatures, the microwave dielectric properties and chemical resistance of the ceramics were investigated. The CaZrB2O6 ceramics with 3 wt% Bi2O3–CuO addition could be sintered below 925°C, and the microwave dielectric properties of the low-temperature samples were ɛr=10.55, Q × f =87,350 GHz, and τf=+2 ppm/°C. The chemical resistance test result showed that both CaZrB2O6- and Bi2O3–CuO-added CaZrB2O6 ceramics were durable in basic solution but were degraded in acid solution.  相似文献   

14.
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 K0.5Na0.5NbO3 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   

15.
(1− x )K0.5Na0.5NbO3– x K3Li2Nb5O15 (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   

16.
Lead-free (K0.44Na0.52Li0.04) (Nb0.96−xTaxSb0.04)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   

17.
Grain growth in a high-purity ZnO and for the same ZnO with Bi2O3 additions from 0.5 to 4 wt% was studied for sintering from 900° to 1400°C in air. The results are discussed and compared with previous studies in terms of the phenomenological kinetic grain growth expression: G n— G n0= K 0 t exp(— Q/RT ). For the pure ZnO, the grain growth exponent or n value was observed to be 3 while the apparent activation energy was 224 ± 16 kJ/mol. These parameters substantiate the Gupta and Coble conclusion of a Zn2+ lattice diffusion mechanism. Additions of Bi2O3 to promote liquidphase sintering increased the ZnO grain size and the grain growth exponent to about 5, but reduced the apparent activation energy to about 150 kJ/mol, independent of Bi2O3 content. The preexponential term K 0 was also independent of Bi2O3 content. It is concluded that the grain growth of ZnO in liquid-phase-sintered ZnO-Bi2O3 ceramics is controlled by the phase boundary reaction of the solid ZnO grains and the Bi2O3-rich liquid phase.  相似文献   

18.
When a small amount of CuO was added to (Na0.5K0.5)NbO3 (NKN) ceramics sintered at 960°C for 2 h, a dense microstructure with increased grains was developed, probably due to liquid-phase sintering. The Curie temperature slightly increased when CuO exceeded 1.5 mol%. The Cu2+ ion was considered to have replaced the Nb5+ ion and acted as a hardener, which increased the E c and Q m values of the NKN ceramics. High piezoelectric properties of k p=0.37, Q m=844, and ɛ3 T 0=229 were obtained from the specimen containing 1.5 mol% of CuO sintered at 960°C for 2 h.  相似文献   

19.
As a candidate for lead-free piezoelectric materials, Li2O-excess 0.95(Na0.5K0.5)NbO3–0.05LiTaO3 (NKN–5LT) ceramics were developed by a conventional sintering process. The sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN–5LT ceramics was observed with varying Li2O content. This grain-growth behavior was explained in terms of interface reaction-controlled nucleation and growth. In the 1 mol% Li2O excess NKN–5LT samples sintered at 1000°C for 4 h in air, the electromechanical coupling factor and the piezoelectric constant of NKN–5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively.  相似文献   

20.
Bi2O3 was added to a nominal composition of Zn1.8SiO3.8 (ZS) ceramics to decrease their sintering temperature. When the Bi2O3 content was <8.0 mol%, a porous microstructure with Bi4(SiO4)3 and SiO2 second phases was developed in the specimen sintered at 885°C. However, when the Bi2O3 content exceeded 8.0 mol%, a liquid phase, which formed during sintering at temperatures below 900°C, assisted the densification of the ZS ceramics. Good microwave dielectric properties of Q × f =12,600 GHz, ɛr=7.6, and τf=−22 ppm/°C were obtained from the specimen with 8.0 mol% Bi2O3 sintered at 885°C for 2 h.  相似文献   

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