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1.
Low-temperature sintering of BaTiO3 ceramics using Li2O as sintering aids was investigated with a special influences of Li2O content (0–4?mol%) and sintering temperature (1000–1100°C) on crystalline structure and electrical properties. The sinterability of BaTiO3 ceramics significantly improved by adding Li2O, whose densification sintering temperature reduced from 1300°C to 1000°C. XRD pattern indicated that BaTiO3-xLi2O samples were single phase with a tetragonal symmetry as x?=?00.3?mol%, while the samples became an orthorhombic symmetry as x?=?0.5–4?mol%. The densification sintering temperature in which samples showed relative density higher than 90?% decreased with increasing Li2O content. A maximum d 33 value (200 pC/N) was obtained for the BaTiO3-0.5?mol%Li2O sample sintered at 1050°C, which is attributed to a vicinity of the phase transition and the high density. Adding Li2O not only reduced the sintering temperature but also obtained the acceptable piezoelectric properties, which will make BaTiO3 become a kind of promising and practical lead-free piezoelectric ceramics.  相似文献   

2.
Abstract

Lead-free 0.88BaTiO3–(0.12-x)BaZrO3xCaTiO3 (BT-BZ-xCT) ceramics were fabricated via solid state reaction. The effect of CaTiO3 content on crystal structure, phase transition, and electrical properties was investigated systematically. The crystal structure and phase transition of ceramics were characterized by X-ray diffraction (XRD), Raman spectra and dielectric measurement. Results show that ceramic in the composition, x?=?0.02, exhibits a rhombohedral structure. Ceramics with increasing CT content transformed from a rhombohedral to orthorhombic structure in the composition, x?=?0.04, and eventually became a tetragonal structure at the composition, x?≥?0.08. The polymorphic phase boundary (PPB) was observed at the composition, x?=?0.06, with coexistence of orthorhombic and tetragonal phases showing at almost room temperature. This PPB composition exhibited a high piezoelectric response (d33*) of 1,150?pm/V at 10?kV/cm as an electric field was applied. These results indicate that the materials studied have potential as candidates for lead-free piezoelectric ceramics.  相似文献   

3.
In this study, to develop the optimal composition of ceramics for low loss piezoelectric actuator and ultrasonic motor applications, (K0.5Na0.5)(Nb0.97Sb0.03)O3?+?0.009 K5.4Cu1.3Ta10O29?+?0.1wt%Li2CO3?+?xwt%Bi2O3(x?=?0?~?0.9) lead-free piezoelectric ceramics with a fixed quantity of 0.009 K5.4Cu1.3Ta10O29 (abbreviated as KCT) were manufactured using the conventional solid-state solution processes. The effects of Bi2O3 addition on the dielectric and piezoelectric properties were then investigated. From the X-ray diffraction analysis result the specimens demonstrated orthorhombic symmetry when Bi2O3 was less 0.6?wt%, a pseudo-cubic phase appeared when Bi2O3 was 0.9?wt%. SEM images indicate that a small amount of Bi2O3 addition affect the microstructure. The piezoelectric properties of (K0.5Na0.5)(Nb0.97Sb0.03)O3 ceramics were greatly improved by a certain amount of Bi2O3 addition. Excellent properties of density?=?4.54?g/cm3, relative densities?=?98.5?%, k p?=?0.468, Q m?=?1,715 and d 33?=?183 pC/N were obtained with a composition of 0.3?wt% Bi2O3  相似文献   

4.
Ferroelectric Glass-ceramics of the Na2O–BaO–Nb2O5–SiO2 system were obtained from controlled crystallization process performed on the parent glass of composition (24-x)Na2O-xBaO-26Nb2O5-50SiO2 where x?=?4 was selected. Nd2O3 doping was applied in the range 0–3 mol%. X-ray diffraction analysis indicated that NaNbO3 and NaBa2Nb5O15 crystals formed as two main crystalline phases. Their relative intensities varied with treatment temperature. Crystalline sizes of both NaNbO3 and NaBa2Nb5O15 calculated from XRD peak broadening were in nanoscale range. Increasing of doping content also gave a parent glass with higher bulk density. The dielectric constant measured at room temperature for glass-ceramic samples was found to be sensitive to the presence of NaBa2Nb5O15 phase. The results of the present work suggest that introduction of Nd3+ into Na2O-BaO-Nb2O5-SiO2 system not only alters the dielectric response but also changes the phase transition behaviors of the co-existant ferroelectric phases by suppressing the growth of the NaBa2Nb5O15 crystals.  相似文献   

5.
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   

6.
A 0.655Pb(Mg1/3Nb2/3)O3-0.345PbTiO3 (PMN-0.345PT) functionally graded (FG) piezoelectric actuator was fabricated by tape-casting. The effects of sintering temperature on the physical and electrical properties of the PMN-PT ceramics were initially investigated. High dielectric and piezoelectric properties of d 33?=?700pC/N, k p?=?0.61, ??r?=?4.77?×?103, tan???=?0.014, P r?=?30.68 ??C/cm2 were obtained for the specimens sintered at 1200°C. Compared with the traditional solid-state reaction, the properties of the ceramics were significantly enhanced by tape-casting. The new FG piezoelectric actuator consisted of four layers, and the variation of changes in their d 33 and ?? r were graded opposite the thickness direction. The relationship between displacement and voltage for the actuator was also determined, with the results showing that it was linear. The driving displacement of the free end of the actuator reached 430.668 ??m.  相似文献   

7.
Compositons in the pseudoquaternary system, 1-×(0.35Bi(Mg1/2Ti1/2)O3-0.30BiFeO3-0.35BiScO3)—×PbTiO3 were fabricated and characterised at the morphotropic phase boundary (MPB) between ferroelectric rhombohedral and tetragonal phases. The MPB occurred at ×?≈?0.48 at which composition the ferreoelectric to paraelectric phase transition, TC?=?450°C, the piezoelectric constant, d33?=?328 pC/N and electromechanical coupling factor, kp?=?0.44. The piezoelectric properties are viable for actuator applications but lower than equivalent high TC piezoelectrics such as 0.36BiScO3–0.64PbTiO3 (d33?=?450 pC/N, TC?=?450°C). However, the relative reduction in the Sc2O3 content gives a significant cost saving which may prove a commercial advantage.  相似文献   

8.
Tungsten doped CaBi4Ti4O15 (CBT) ceramics was prepared by solid-state reaction method. A pure single phase of layer-structured ferroelectric with m?=?4 was formed when x?≤?0.025. The effect of W doping on dielectric, ferroelectric and piezoelectric properties was investigated. W6+ doping increased the temperature stability of dielectric constant and decreased dielectric loss. W6+ doping decreased the remanent polarization, while the coercive field decreased as well, as a result, the piezoelectric constant was increased. AC conductivity measurement showed that W6+ doping increased the conductivity of CBT ceramics and showed n-type conducting mechanism. W6+ doped ceramics has smaller activation energy due to many defects introduced in the crystal lattice.  相似文献   

9.
10.
采用类似溶胶-凝胶法合成稀土金属氧化物Dy2O3掺杂LiDyxMn2-xO4(x=0,0.01,0.02,0.05).通过XRD和恒流充放电测试了稀土金属元素Dy的掺杂对正极材料的结构以及电化学性能的影响.研究结果表明:当掺杂量x=0.02时,材料LiDy0.02Mn1.98O4具有较高的初始比容量(109mAh/g)和循环性能,50次循环后,容量保持率为95%.  相似文献   

11.
Crystallizable zinc borate glasses modified with different contents of La2O3 or Nd2O3 were investigated as a potential low loss dielectric with respect to their crystallization behavior and microwave dielectric characteristics. The glasses were admixed with Al2O3 filler and fired at 850°C for 30 min in air to prepare low temperature dielectrics. Crystallization behavior and microwave dielectric properties of the resulting samples strongly depended on the relative content of La2O3 or Nd2O3 in the glass. As a promising result, the composition of 0.15ZnO-0.25Nd2O3-0.6B2O3 exhibited k?~?6.5 and Q?~?1194 at the resonant frequency of 18.9 GHz. Near zero temperature coefficient of frequency (TCF) was obtained by additional modification of the composition with ~10 wt.% of TiO2 filler. Crystallization kinetics of the samples was studied based on the differential thermal analysis (DTA) curves obtained with different heating rates. Correlation of the observed dielectric properties to the crystallization behavior is the main subject of this work.  相似文献   

12.
In this paper, the structural and dielectric properties of SrBi2Nb2O9 (SBN) as a function of Bi2O3 or La2O3 addition level in the radio (RF) and microwave frequencies were investigated. The SBN, were prepared by using a new procedure in the solid-state reaction method with the addition of 3; 5; 10 and 15 wt.% of Bi2O3 or La2O3. A single orthorhombic phase was formed after calcination at 900 °C for 2 h. The analysis by x-ray diffraction (XRD) using the Rietveld refinement confirmed the formation of single-phase compound with a crystal structure (a?=?5.5129 Å, b?=?5.5183 Å and c?=?25.0819 Å; α?=?β?=?γ?=?90°). Scanning Electron Microscope (SEM) micrograph of the material shows globular morphologies (nearly spherical) of grains throughout the surface of the samples. The Curie temperature found for the undoped sample was about 400 °C, with additions of Bi3+, the temperature decreases and with additions of La3+ the Curie temperature increased significantly above 450 °C. In the measurements of the dielectric properties of SBN at room temperature, one observe that at 10 MHz the highest values of permittivity was observed for SBN5LaP (5%La2O3) with values of 116,71 and the lower loss (0.0057) was obtained for SBN15LaP (15%La2O3). In the microwave frequency region, Bi2O3 added samples have shown higher dielectric permittivity than La2O3 added samples, we highlight the SBN15BiG (15 % Bi2O3) with the highest dielectric permittivity of 70.32 (3.4 GHz). The dielectric permittivity values are in the range of 28–71 and dielectric losses are of the order of 10?2. The samples were investigated for possible applications in RF and microwave components.  相似文献   

13.
The effects of CuO and TiO2 additives on the microstructure and microwave dielectric properties of Al2O3 ceramics were investigated. Al2O3 ceramics with CuO and TiO2 additions can be well sintered to achieve 93∼98% theoretical densities below 1,360 °C due to Ti4Cu2O liquid phase sintering effect. The Qf values decreased with increasing CuO and TiO2 content, due to the formation of the second phase Ti4Cu2O. However, the varying behaviors of the dielectric constant (ɛ r ) and temperature coefficients (τ f ) were associated with phase constitutions, as a result of the change of CuO and TiO2content. The τ f can be shifted close to 0 ppm/°C by controlling the content of CuO and TiO2. The specimens with 0.5 wt.% CuO and 7 wt.% TiO2 sintered at 1,360 °C for 4 h showed ɛ r of 11.8, Qf value of 30,000 GHz, and τ f of −7 ppm/°C.  相似文献   

14.
In this paper, we systematically investigated the effect of microwave sintering parameters on the characteristics of BaTiO3 capacitor materials co-doped with Y2O3/MgO species. It is observed that the granular structure of the materials is relatively insensitive to the sintering temperature and soaking time such that the BaTiO3 capacitor materials possessing X7R dielectric constant-temperature (K-T) characteristics can be obtained in a wide range of sintering conditions. TEM examinations reveal that the detailed microstructure of these materials is extremely complicated. The unique K-T properties of these materials are ascribed to the duplex structure of the samples, viz. fine grains of paraelectric phase and large grains of ferroelectric phase.  相似文献   

15.
A conventional BaO–Nd2O3–TiO2 ceramic of microwave dielectric material was added to rare-earth derived borate glasses (La2O3–B2O3–TiO2) for use as LTCC (low temperature co-fired ceramic) materials. The sintering behavior, phase evaluation, and microwave dielectric properties were investigated. It was found that increasing the sintering temperature from 750 to 850 °C led to increases in shrinkage and microwave dielectric properties (≈15 for ?r , >10,000 GHz for Q*f0 and >94 ppm/ °C for τ f at 7–8 GHz for resonant frequency). The results suggest that a composite with suitable additives for τ f could feasibly be developed as a material for LTCC applications.  相似文献   

16.
Piezoelectric properties of Al2O3-doped Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramics were investigated. The constituent phases, microstructure, electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants were analyzed. Diffraction peaks for (002) and (200) planes were identified by X-ray diffractometer for all the specimens doped with Al2O3. The highest sintered density of 7.8 g/cm3 was obtained for 0.2 wt% Al2O3-doped specimen. Grain size increased by doping Al2O3 up to 0.3 wt%, and it decreased by more doping. Electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants increased by doping Al2O3 up to 0.2 wt%, and it decreased by more doping. This might result from the formation of oxygen vacancies due to defects in O2 − ion sites and the substitution of Al3+ ions.  相似文献   

17.
The effect of Sr doping on the transport and magnetism properties of charge/orbital-ordered Nd0.55Ca0.45MnO3 is investigated. A low temperature phase transition from a charge/orbital ordered insulator to a ferromagnetic metal was founded in the Nd0.55(Ca1?x Sr x )0.45MnO3 samples. The ground state is the charge/orbital ordered insulator at x?<?0.2, while for x?>?0.3 it changes to a ferromagnetic metal. The resistivities of the samples exhibit almost ideal percolation behavior with a percolation threshold of 0.3. Therefore, this system shows an intricate competition between metallic ferromagnetism and charge/orbital ordered insulator and the percolation behavior demonstrates that the relative volumes of ferromagnetic phase and charge/orbital phases changes with the doping content x and temperature.  相似文献   

18.
Eu doped Y2O3 particles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The Eu doped Y2O3 particles were obtained at 270°C. The average particle size of synthesized powders was below 1 um. The X-ray diffraction pattern shows that the synthesized particles were crystalline. This study has shown that the synthesis of Eu doped Y2O3 crystalline particles is possible under glycothermal conditions in ethylene glycol solution. The effects of synthesis parameters, such as the concentration of starting solution, pH of starting solution, reaction temperature and time, are discussed.  相似文献   

19.
Nd2O3掺杂对NiZn铁氧体电磁性能的影响   总被引:1,自引:0,他引:1  
研究了Ni0.4Zn0.6NdxFe2-xO4铁氧体的电磁性能,从材料的微观结构出发,着重讨论了Nd^3+离子对NiZn铁氧体起始磁导率μ,品质因素Q,截止频率fc电阻率ρ以及居里温度TC的影响。  相似文献   

20.
Detailed microstructure of MgO/Y2O3 co-doped BaTiO3 materials were examined using transmission electron microscopy (TEM). For the 1250_C-sintered BaTiO3 samples possessing flat K-T characteristics, which meet the X7R specification, the granular structure is complicated. Most of the grains are very small ( 150 nm) and are highly strained. The small grains contain large proportion of Y2O3 species and are paraelectric, whereas the large grains contain Y2O3 species unevenly distributed and are of core-shell structure. In contrast, for the 1300C-sintered BaTiO3 samples, which have K-T properties slightly off the X7R specification, the grains grew larger to around 300 nm. The core-shell structured grains are seldom observed. Apparently, it is the existence of such a non-equilibrium core-shell microstructure, which renders the dielectric properties of the BaTiO3 materials extremely sensitive to the processing parameters.  相似文献   

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