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1.
The ternary lead-free piezoelectric ceramics system of (1 – x) [0.88Na0.5Bi0.5TiO3-0.12K0.5Bi0.5TiO3] – xNaNbO3(x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized by conventional solid state reaction method. The crystal structure, dielectric, piezoelectric properties and P-E hysteresis loops were investigated. The crystalline structure of all compositions is mono-perovskite phase ascertained by XRD, and the lattice constant was calculated from the XRD data. Temperature dependence of dielectric constant r and dissipation factor tan measurement revealed that all compositions experienced two phase transitions: from ferroelectric to anti-ferroelectric and from anti-ferroelectric to paraelectric, and these two phase transitions have relaxor characteristics. Both transition temperatures Td and Tm are lowered due to introduction of NaNbO3. P-E hysteresis loops show that 0.88Na0.5Bi0.5TiO3-0.12K0.5Bi0.5TiO3 ceramics has the maximum Pr and Ec corresponding to the maximum values of electromechanical coupling factor Kp and piezoelectric constant d33. The piezoelectric constant d33 and electromechanical coupling factor Kp decrease a little, while the dielectric constant 33T/0 improves much more when the concentration of NaNbO3 is 8 mol%.  相似文献   

2.
Three primary differences between BNT- and PZT-based ceramics were analyzed from the composition and the active component of the materials. Based on the analysis the authors’ group developed the new idea of the design of the multiple complex in the A-site ions of BNT compounds. (Bi0.5Na0.5)2+, Bi3+ and Na+ in the ABO3 structure are defined as A-site, A1-site and A2-site ions, respectively, and A, A1 and A2-site ions can be simultaneously or singly substituted partially by alkaline-earth metal ions, metal ions with +3 valence and metal ions with +1 valence, respectively. Under this consideration, Several new systems of Bi0.5Na0.5TiO3 (abbreviated as BNT)-based lead-free piezoelectric ceramics were proposed. These ceramics can be prepared by conventional ceramic techniques and have excellent piezoelectric performance. Among these materials, Bi0.5(Na1−xy K x Li y )0.5TiO3 possesses higher piezoelectric constant (d 33 = 230 pC/N), higher electromechanical couple factor (k p = 0.40), larger remanent polarization (P r = 38.9 μC/cm2) and a better P-E hysteresis loop until about 200C. This work was supported by the projects of NSFC (50410179), (50572066), and (59972020), and NAMMC (2001-AA325060).  相似文献   

3.
The important properties of lead-free piezoelectric ceramics have been investigated from Bismuth Sodium Lanthanum Titanate and Barium Titanate system: (1 − y)(Bi0.5Na0.5)(1 − 1.5x)La x TiO3(BNLT)—yBaTiO3(BT) where x = 0.017 and y = 0 − 0.2, respectively. The morphotropic phase boundary (MPB) was found to be around y = 0.1 by the x-ray diffraction and dielectric measurement at various amount of BT. The temperature dependence of dielectric constant (ε r ) at various value of y showed the diffuse phase transition exhibiting the relaxor type ferroelectrics. The degree of diffuseness increased at a high doping content of about y = 0.15 where the second phase transition (T2) of the ferroelectric to antiferroelectric phase disappeared. Moreover, this sample had the maximum piezoelectric coefficient (d 33) of about 112 pC/N with relatively low dielectric constant. The optimum sintering temperatures and the microstructures of the dense BNLT-BT ceramics were also examined.  相似文献   

4.
Electrical properties and sintering behaviors of (1 − x)Pb(Zr0.5Ti0.5)O3-xPb(Cu0.33Nb0.67)O3 ((1 − x)PZT-xPCN, 0.04 ≤ x ≤ 0.32) ceramics were investigated as a function of PCN content and sintering temperature. For the specimens sintered at 1050C for 2 h, a single phase of perovskite structure was obtained up to x = 0.16, and the pyrochlore phase, Pb2Nb2O7 was detected for further substitution. The dielectric constant (ε r), electromechanical coupling factor (Kp) and the piezoelectric coefficient (d 33) increased up to x = 0.08 and then decreased. These results were due to the coexistence of tetragonal and rhombohedral phases in the composition of x = 0.08. With an increasing of PCN content, Curie temperature (Tc) decreased and the dielectric loss (tanδ) increased. Typically, εr of 1636, Kp of 64% and d33 of 473pC/N were obtained for the 0.92PZT-0.08PCN ceramics sintered at 950C for 2 h.  相似文献   

5.
Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi1/2Na1/2)TiO3(BNT)-based solid solution, that is, (Bi1/2Na1/2)(1-x)(Pba Bab)xTiO3(a + b = 1) [BNPB(100x-100a/100b)], are studied from the viewpoint of a new group of lead-free or low-lead content piezo-electric ceramics with a rhombohedral(Fa-tetragonal (Fβ) morphotropic phase boundary (MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling. X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi1/2Na1/2)TiO3[BNT] at x = 0.13–0.14, 0.08–0.09 and 0.06–0.07 in the case of b = 0, b = 0.5 and b = 1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high-frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity ε33Tε0, and a high electromechanical coupling factor k33, along with a high mechanical strength.  相似文献   

6.
The piezoelectric properties of a solid solution based on three components of bismuth sodium titanate (Bi1/2Na1/2)TiO3 (BNT), bismuth potassium titanate, (Bi1/2K1/2)TiO3 (BKT), and barium titanate, BaTiO3 (BT), that is x(Bi1/2Na1/2)TiO3y(Bi1/2K1/2)TiO3zBaTiO3, [, abbreviated as BNBKy:z(x)] and potassium niobate, KNbO3 (KN) based ceramics, that is KN+MnCO3 x wt.%, [abbreviated as KN−Mn x], were studied as a lead-free piezoelectric material. In the case of BNBK2:1 system, high piezoelectric properties were obtained near the MPB composition, and the highest electromechanical coupling factor, k 33 and piezoelectric constant, d 33, were 0.58 for BNBK2:1(0.89) and 181 pC/N for BNBK2:1(0.88). Nevertheless, the depolarization temperature, T d , shifts to lower temperature around the MPB compositions, and the T d ’s of BNBK2:1(0.88–0.90) are only about 100 °C. On the tetragonal side, the T d shifts to higher temperature with increasing the lattice anisotropy, c/a. As T d higher than 200 °C was obtained in the range of x < 0.78, with a k 33 and d 33 for BNBK2:1(0.78) being 0.45 and 128 pC/N, respectively. In the case of Mn doped KN ceramics, dense and non deliquescence KN ceramic were successfully obtained via ordinary firing technique in air by optimizing the fabrication process. Mn doping for KN ceramics was effective to obtain full poling state easily under poling conditions of high temperature and high electric field. As a result, we obtained the excellent piezoelectric properties of k 33 = 0.507 for KN−Mn0.2.  相似文献   

7.
Ceramics in the xPb(Zn1/3Nb2/3)O3−(1−x)Pb(Zr0.5Ti0.5)O3 [xPZN–(1−x)PZT] solid solution system are expected to display excellent dielectric, piezoelectric, and ferroelectric properties in compositions close to the morphotropic phase boundary (MPB). The dielectric behavior of ceramics with x = 0.1−0.6 has been characterized in order to identify the MPB compositions in this system. Combined with X-ray diffraction results, ferroelectric hysteresis measurements, and Raman reflectivity analysis, it was consistently shown that an MPB exists between x = 0.2 and x = 0.3 in this binary system. When x ≤ 0.2, the tetragonal phase dominates at ambient temperatures. In the range of x ≥ 0.3, the rhombohedral phase dominates. For this rhombohedral phase, electrical measurements reveal a profound frequency dispersion in the dielectric response when x ≥ 0.6, suggesting a transition from normal ferroelectric to relaxor ferroelectric between 0.5 ≤ x ≤ 0.6. Excellent piezoelectric properties were found in 0.3PZN–0.7PZT, the composition closest to the MPB with a rhombohedral structure. The results are summarized in a PZN–PZT binary phase diagram.  相似文献   

8.
Ceramics of 0.2CaTiO3-0.8Li0.5Nd0.5TiO3) have been prepared by the mixed oxide route using additions of Bi2O3-2TiO2 (up to 15 wt%). Powders were calcined 1100C; cylindrical specimens were fired at temperatures in the range 1250–1325C. Sintered products were typically 95% dense. The microstructures were dominated by angular grains 1–2 μm in size. With increasing levels of Bi2O3-2TiO2 additions, needle and lath shaped second phases developed. For Bi2Ti2O7 additions up to 5 wt%, the relative permittivity increased from 95 to 131, the product of dielectric Q value and measurement frequency increased from 2150 to 2450 GHz and the temperature coefficient of resonant frequency (τ f ) increased from −28pp/C to +22pp/C. A product with temperature stable τ f could be obtained at ∼2 wt% Bi2Ti2O7 additions. For high levels of additives, there is minimal change in relative permittivity, the Qxf values degrade and τ f becomes increasingly negative.  相似文献   

9.
Dielectric and piezoelectric properties of grain oriented (Bi0.5Na0.5)TiO3-BaTiO3 ceramics were investigated in a process that the templated grain growth and hot pressing methods were employed. A ceramic composition in Bi-based perovskite structure family, (Bi0.5Na0.5)TiO3-BaTiO3, was chosen as a matrix material and plate shaped SrTiO3 as a template. To examine the combined process effect on piezoelectric properties, three processes, conventional solid reaction, templated grain growth and the combine treatment of templated grain growth and hot-pressing, were compared. Specimen processed by templated grain growth and hot pressing methods exhibited better piezoelectric coefficient, d 31 (−79.6 pC/N) and electromechanical coefficient, k 33 (0.35) than those of the other specimens, fabricated by solid reaction and templated grain growth, respectively. The improved properties were attributed to reduction of pore existing in matrix, which is related to abnormal grain growth from SrTiO3 template and its resultant heterogeneous shrinkage.  相似文献   

10.
BaPbO3 ceramics has attracted considerable interest due to the promising electrical applications. For the best control of the microstructure and phase, Sb-doped BaPbO3 ceramics were prepared by a sol-gel route. Inorganic compounds were used as starting chemicals, citric acid and Ethylene diamine tetra-acetic acid (EDTA) as complex chelate agent, and distilled water as solvent. Experimental results demonstrate that the Sb-doped BaPbO3 ceramics with homogeneous composition could be prepared by the method mentioned above. Influence of Pb/Ba ratio and Sb concentration on the room-temperature resistivity and the PTCR behavior of BaPb1+xy Sb y O3 (x = 0.0, 0.1, 0.2 and 0 ≤ y ≤ 0.2) compositions was investigated. The PTCR behavior was related to the Pb/Ba ratio and major compensating defect in BaPbO3. The lowest electrical resistivity of Sb-doped BaPbO3 was calculated to be 2.69 × 10−4 Ω·cm when the Sb concentration y = 12–13 mol%. The 0.5 mol% Sb-doped BaPbO3 showed the best PTCR behavior, and its Curie temperature is about 850 °C.  相似文献   

11.
Lead-free piezoelectric ceramics (1 − x)(K0.5Na0.5)NbO3xLiNbO3 (abbreviated an KNLN) have been synthesized by traditional ceramics process. Effects of heating rate on the phase structure, microstructure evolution and piezoelectric properties of (1 − x)(K0.5Na0.5)NbO3xLiNbO3 were investigated. Results show that the heating rate has no effects on the phase structures. However, the fracture surface of the 0.94(K0.5Na0.5)NbO3 −0.06 LiNbO3 ceramics transforms from intergranular fracture mode to a typical transgranular fracture mode with the increasing of the heating rate. This result is ascribed to the presence of agglomerates of grains which exhibit different sintering behavior at diverse heating rates. The 0.94(K0.5Na0.5)NbO3–0.06LiNbO3 ceramic sintered at 1080°C with heating rate of 5°C/min shows the optimum piezoelectric properties(d 33 = 210 pC/N, k p = 0.403 and k t = 0.498).  相似文献   

12.
BaO ⋅ Nd2O3 ⋅ 4TiO2—based ceramics were prepared by the mixed oxide route. Specimens were sintered at temperatures in the range 1200–1450C. Microstructures were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM); microwave dielectric properties were determined at 3 GHz by the Hakki and Coleman method. Product densities were at least 95% theoretical. The addition of up to 1 wt% Al2O3 to the starting mixtures reduced the sintering temperatures by at least 100C. Incorporation of small levels of Al into the structure (initially Ti sites) led to an increase in Q × f values, from 6200 to 7000 GHz, a decrease in relative permittivity (εr) from 88 to 78, and moved the temperature coefficient of resonant frequency (τf) towards zero. The addition of 0.5 wt% Al2O3 with 8 wt% Bi2O3 improved densification, increased both εr (to 88) and Q× f (to 8000 GHz) and moved τf closer to zero. Ceramics in the system (1 − x)BaO ⋅ Nd2O3 ⋅ 4TiO2 + xBaO ⋅ Al2O3 ⋅ 4TiO2 exhibited very limited solid solubility. The end member BaO ⋅ Al2O3 ⋅ 4TiO2 was tetragonal in structure with the following dielectric properties: εr = 35; Q× f = 5000 GHz; τf = −15ppm/C. Microstructures of the mixed Nd-Al compositions contained two distinct phases, Nd-rich needle-like grains and large Al-rich, lath-shaped grains. Products with near zero τf were achieved at compositions of approximately 0.14BaO ⋅ Nd2O3 ⋅ 4TiO2 + 0.86BaO ⋅ Al2O3 ⋅ 4TiO2, where Q× f = 8200 GHz and εr = 71.  相似文献   

13.
In this letter, MnO2-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT-6) lead-free piezoelectric ceramics were synthesized by solid state reaction, and the microstructure and electrical properties of the ceramics were investigated. X-ray diffraction (XRD) reveals that all specimens take on single perovskite type structure, and the diffraction peaks shift to a large angle as the MnO2 addition increases. Scanning electron microscopy shows that the grain sizes increases, and then decreases with increasing the MnO2 content. The experiment results indicate that the electrical properties of ceramics are significantly influenced by the MnO2 content, and the ceramics with homogeneous microstructure and excellent electrical properties are obtained with addition of 0.3 wt% MnO2 and sintered at 1160°C. The piezoelectric constant (d33), the electromechanical coupling factor (k p ), the dissipation factor (tan δ) and the dielectric constant (ɛ r ) reach 160 pC/N, 0.29, 0.026 and 879, respectively. These excellent properties indicate that the MnO2-doped BNBT-6 ceramics can be used for actuators.  相似文献   

14.
Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.92(Ba0.8Sr0.2)0.08 TiO3+x mol% La2O3(x = 0, 0.1, 0.3, 0.5, 0.8) were synthesized by conventional solid state reaction. The crystal structure of all compositions is mono-perovskite ascertained by XRD. The grain size decreased and diffuse phase transition behavior was more evident with the increasing amount of La2O3. The piezoelectric constant d33 and the electromechanical coupling factor kp showed the maximum value of 165 pC/N and 0.322 at 0.3% and 0.1% La2O3 addition, respectively, and rapidly decreased when La2O3 addition over 0.5%. The loss tangent tanδ linearly increased and the mechanical quality factor Qm linearly decreased with the increasing amount of La2O3.  相似文献   

15.
In this article, (Na0.5Bi0.5)1-xBaxTiO3 lead-free piezoelectric ceramics were prepared by solid-state reaction. The influence of Ba contents on phase structures, compositional distribution and electrical properties of (Na0.5Bi0.5)1-xBaxTiO3 ceramics were systematically investigated to further understand the nature of phase transition. It was found that the phase structure of (Na0.5Bi0.5)1-xBaxTiO3 transforms from rhombohedral to tetragonal symmetry at x = 0.06 ~ 0.07 and Ba2+ segregation forms the coexistence of Ba-rich tetragonal and Ba-deficient rhombohedral phases close to MPB. The electrical properties of prepared samples regularly changed with Ba content, which is closely related to the distribution of rhombohedral and tetragonal phases. The prepared sample near MPB exhibited the largest dielectric constant and the excellent piezoelectric properties (the maximal measuring field reached 78 kV/cm and the piezoelectric constant d 33 = 151pC/N).  相似文献   

16.
The piezoelectric properties of (1?x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics were reported and their piezoelectric properties reach extreme values near the MPB (about x?=?0.06). The X-ray analysis of (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics for all compositions exhibited a pure perovskite structure without any secondary phase. Within a certain ratio of contents, the co-doped ceramics enhanced piezoelectric coefficient (d 33 ), lowered the dielectric loss, and increased the sintered density. The temperature dependence of relative dielectric permittivity (K 33 T ) reveals that the solid solutions experience two phase transitions, ferroelectric to anti-ferroelectric and anti-ferroelectric to relaxor ferroelectric, which can be proven by P-E hysteresis loops at different temperatures. In addition, the specimen containing 0.04/0.01 wt.% CaO/MnO showed that the coercive field E c was a minimum value of 26.7 kV/cm, while the remnant polarization P r was a maximum value of 38.7 μC/cm2, corresponding to the enhancement of piezoelectric constant d33 of 179 pC/N, electromechanical coupling factor k p of 37.3%, and relative dielectric permittivity K 33 T of 1137. (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics co-doped with CaO/MnO were considered to be a new and promising candidate for lead-free piezoelectric ceramics owing to their excellent piezoelectric/dielectric properties, which are superior to an un-doped BNBT system.  相似文献   

17.
The effects of Mn-doping on TSDC (Thermally Stimulated Depolarization Current) and electrical degradation of BaTiO3 have been investigated. TSDCs of un-doped BaTiO3 and Ba(Ti1−x Mnx)O3−δ exhibited the three sharp TSDC peaks around phase transition temperatures. TSDC of Ba(Ti0.995Mg0.005)O2.995 increased gradually from 50C and this anomalous depolarization current kept going up well above the Curie temperature (∼130C). TSDCs of un-doped BaTiO3 and Ba(Ti0.995Mn0.005)O3−δ decreased in the temperature range above the Curie point, whereas a slight increase in TSDC was confirmed at the specimen of Ba(Ti0.99Mn0.01)O3−δ. TSDCs of Ba(Ti0.995−y Mg0.005Mny)O3−δ (y = 0.005, 0.01) were lower than that of Ba(Ti0.995Mg0.005)O2.995.  相似文献   

18.
The electric mechanisms of perovskite-type LaMnO3 was investigated with B-site substitution in this paper. Samples of La(TixMn1 − x)O3 (0.1 ≰ x ≰ 0.7) were sintered at different temperature. The voltage-temperature (V-T) curves of the samples were tested from room temperature (25C) to 300C, then the electric properties were measured and analyzed. The experimental results showed that the resistivity-temperature (ρ-T) curves of the samples matched NTC characteristic. The resistivity increased slightly with the increase of Ti amount as x was less than 0.5, however, it rose greatly after x exceeded 0.5; The sintering temperatures have a little influence on the resistivity, except for the sample with x = 0.7.  相似文献   

19.
The as-sintered Mn1.1Ni1.4Co0.5O4 crystallized in the solid solution of cubic spinel Mn-Ni-Co oxides, along with a small amount of the cubic spinel Ni-rich oxide phase. On the other hand, the Cr-substituted Mn1.1Ni1.4 Co0.5− x Cr x O4 (0.07 ≤xq 0.35) showed a single phase of cubic spinel Mn-Ni-Co-Cr oxides. This indicates that the substituted Cr suppressed the decomposition in the oxides. In addition, the Cr hindered the grain growth during sintering and increased the porosity. The electrical resistivity, the B 25/85 constant, and the activation energy of the Mn1.1Ni1.4Co0.5− x Cr x O4 NTC thermistors increased with increasing Cr content. It is demonstrated that the Cr-substituted Mn1.1Ni1.4Co0.5− x Cr x O4 NTC thermistors provided a variety of electrical properties, depending on the composition.  相似文献   

20.
A systematic investigation of cerium and stannum doped 0.94(Bi0.5Na0.5)TiO3−0.06BaTiO3 (Sn&Ce-BNT6BT) based lead-free piezoelectric ceramics is undertaken to understand the influence of sintering temperature on electrical properties. The X-ray diffraction patterns showed that all of the Sn&Ce-BNT6BT ceramics exhibited a single perovskite structure with the co-existence of the rhombohedral and tetragonal phase. The smaller grain size of Sn&Ce-BNT6BT ceramics was obtained at lower sintering temperature, and more cubical grains of Sn&Ce-BNT6BT ceramics were obtained at higher sintering temperature. The temperature dependence of dielectric permittivity of the compositions exhibited strong dispersion with the increasing temperature, and the dielectric loss tangent increased dramatically while the temperature over 225C. The depolarization temperature T d of Sn&Ce-BNT6BT ceramics sintered at 1160C was 92.6C. The remnant polarizations P r for Sn&Ce-BNT6BT ceramics sintered at 1120 and 1200C were found to be 28.8 and 33.4 μC/cm2 at room temperature, respectively.  相似文献   

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