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1.
The dielectric properties of the Bi4–x La x Ti3O12 (0 x 2) ceramics were characterized and discussed together with the P-E relation (polarization vs. electric field). With increasing x, the P-E relation changed from normal ferroelectric hysteresis loops to pure linear relation, which indicated that La3+ substitution for Bi3+ in Bi4Ti3O12 induced a phase transition from ferroelectric to paraelectric state at ambient temperature. Low loss dielectric ceramics with temperature stable dielectric constant were obtained for x > 1.2 in Bi4–x La x Ti3O12 at 1 MHz. And the loss increased in all the compositions when the ceramics were measured at microwave frequencies.  相似文献   

2.
Neodymium-modified Bi4Ti3O12, (Bi, Nd)4Ti3O12 (BNT) ferroelectric thin films have been prepared on Pt/TiOx/SiO2/Si substrates using metal-organic precursor solutions by the chemical solution deposition method. The BNT precursor films crystallized into the Bi layered perovskite Bi4Ti3O12 (BIT) as a single-phase above 600C. The synthesized BNT films revealed a random orientation having a strong 117 reflection, whereas non-substituted BIT thin films exhibited a random orientation with strong 00l diffractions. Among Bi4 – xNdxTi3O12 [x = 0.0, 0.5, 0.75, 1.0] thin films, Bi3.25Nd0.75Ti3O12 thin films showed a well-saturated P-E hysteresis loop with the highest Pr (22 C/cm2) and a low Ec (69 kV/cm) at an applied voltage of 5 V. The Nd-substitution with the optimum amount for the Bi site in the BIT structure was effective not only for promoting the 117 preferred orientation but also for improving the microstructure and ferroelectric properties of the resultant films.  相似文献   

3.
Recent work on PZT and BST thin films reveal a thickness dependence of the dielectric constant for a film thickness below 100 nm. This effect is commonly attributed to an interfacial layer between the electrode and the dielectric film (dead layer). In this contribution we report on the influence of the film thickness on the dielectric constant of Ba(TixZr1 – x)O3 thin films with different Zr-contents (x = 0–30 at.%). The films were prepared by chemical solution deposition (CSD) with thickness between 30 and 350 nm.The electrical characterization was performed in a temperature range between 25 and 200C. Results were interpreted with respect to the formation of a serial dead layer capacitance.  相似文献   

4.
Modification of Ba5NdTi3Ta7O30 dielectric ceramics was investigated through introducing Bi4Ti3O12. With increasing of Bi4Ti3O12 content, the dielectric constant increased, and the temperature coefficient of the dielectric constant changed from negative to positive. The small temperature coefficient ( < 50 ppm/°C) combined with high dielectric constant ( = 178) and low dielectric loss (tan = 0.007 at 1 MHz) was achieved in the composition x = 0.6.  相似文献   

5.
Raman spectroscopy was used to study the long wavelength vibrations of tetragonal perovskite (space group P4mm) Pb(HfxTi1–x)O3 (PHT) (0.10 x 0.50) samples at room temperature and at 20 K. For x 0.40, Raman spectra collected from the PHT samples were very similar to the previous spectra collected from the PZT samples with the same value of x, except the mode at around 190 cm–1, whose frequency was decreasing with increasing x in PHT ceramics. Correspondingly, the latter feature was taken as a sign of the mass effect (Hf versus Zr) while the similarity of the remaining parts of the Raman spectra was assumed to be due to the almost identical ionic radii difference between Ti4+ and Zr4+ and between Ti4+ and Hf4+ ionic radii. The behaviour of the mode at around 280 cm–1 revealed that a phase transition occurred once x was changing from 0.40 to 0.50.  相似文献   

6.
The electrical and microstructural properties of (Ba x Sr 1 m x )Ti 1+y O 3+z (BST) thin films prepared by RF magnetron sputtering were investigated as a function of deposition temperature over the range of 100 C to 650 C. Films deposited above approximately 350 C on Pt/TiO 2 /SiO 2 /Si substrates were polycrystalline with relative permittivites of 100 nm thick BST thin films varying from 100 at 350 C to 600 at 650 C. For deposition temperatures below approximately 350 C, the electrical properties were strongly influenced by the presence of a less crystalline BST layer. Films deposited at 250 C were comprised of a multilayer polycrystalline/less crystalline BST structure. The less crystalline BST layer strongly affected both measured dielectric permittivity and leakage properties. Leakage characteristics of Pt/BST(250C)/Pt capacitors exhibited a power law dependence on voltage or an exponential dependence on square root of the applied voltage depending on whether the top Pt electrode adjacent ot the polycrystalline BST layer was biased at a high or low electric potential, respectively. Mechanisms for the observed leakage behavior are discussed.  相似文献   

7.
The dielectric properties and synthesis of pyrochlore-free lead zinc niobate ceramics with Ba substituting for Pb were investigated. Ba partial substitution for Pb was effective in stabilizing the perovskite structure in PZN ceramics, where the minimum amount of Ba substitution needed was about 20 mol%. The dielectric loss and the temperature coefficient of dielectric constant of PZN were reduced markedly with Ba substitution, while the dielectric constant was greater than 110. Good dielectric properties were obtained for the composition of Pb0.3Ba0.7(Zn1/3Nb2/3)O3: = 133.5, tan = 0.0009, = –811 ppm/°C.  相似文献   

8.
Barium zirconate titanate Ba(Zr x Ti1?x )O3 (BZT x?=?0.1, 0.15, 0.2, 0.25) ceramics doped with Nb2O5 have been prepared by a traditional solid phase reaction. The temperature dependence of dielectric permittivity has been investigated. The results show that the phase transition temperature T c is depressed and the diffuse phase transition behavior is enhanced with increasing Zr content. The Cole–Cole plot has been discussed and the cause of the deviation has been analyzed. The temperature dependence of inverse dielectric constants was investigated. A modified Curie–Weiss law can be used to describe the diffuseness of a phase transition, and diffusion factor increases with the Zr content.  相似文献   

9.
In this paper, piezoelectric and dielectric properties of 0.9PbZrxTi1–xO3-0.1PbNi1/3Sb1/3Nb1/3O3 were studied as a function of Zr/Ti mole ratio(x) for application to piezoelectric actuator. Also, microstructure and crystalline phase are investigated by using SEM and XRD, respectively. As a results, the substitution of Sb5+ to B-site increases the piezoelectric and dielectric properties, and when Zr/Ti mole ratio is 49/51 and ternary mole ration is 0.1(0.9PbZr0.49Ti0.51O3-0.1PbNi1/3Sb1/3Nb1/3O3), the corresponding composition were found belonging to the Morphotropic Phase Boundary region with electromechanical coupling coefficient(kp), mechanical quality factor (Qm), permittivity(r) and piezoelectric strain constant(d33) equaled to 63%, 360, 2000 and 470 pC/N, respectively. Sintering temperature was about 1150_C and Curie temperature was determined around 290_C.  相似文献   

10.
Ceramics of bismuth titanate, Bi4Ti3O12 (BIT) and the La-doped series, Bi4?x La x Ti3O12 (xBLT) with x?=?0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.75, have been synthesized by a new sol-gel process based on ethylene glycol. La-doping is found to reduce the temperature of the formation of pure Bi-layer-structured phase from 600 °C in BIT and low La-doped xBLT (x?=?0.1–0.3) to 500 °C in high La-doped xBLT (x?=?0.4–0.75). Increasing the La-content in the xBLT ceramics decreases the contribution of the space charge polarization to the apparent dielectric permittivity. The ceramics of xBLT prepared by this sol-gel route exhibit improved dielectric properties, with a higher room temperature dielectric constant and lower losses up to high temperatures.  相似文献   

11.
The electrical properties of BaO-Nd2O3-Sm2O3-TiO2 ceramics doped with low loss glass or low melting point oxide B2O3 are evaluated by impedance spectroscopy. Glass or B2O3 is doped as liquid phase sintering aid. Doping of glass/B2O3 enhances both the growth in the longitudinal direction of the columnar crystal and the preferred orientation of (002). The grain size increases and grain boundary decreases with the increase of dopant. Both the grain and grain-boundary resistivities decrease with the increase of dopant. The grain boundary activation energy for charge transport is larger than that of the grain activation energy. Possible mechanisms for the electrical behavior of the liquid-phase sintered BaO-Nd2O3-Sm2O3-TiO2 ceramics are proposed and discussed.  相似文献   

12.
Ba(Zn1/3X2/3)O3 materials where X = Ta or Nb (respectively named BZT and BZN) exhibit attractive properties suitable for applications in type I Multi Layer Ceramics Capacitors (MLCC). Nevertheless, to produce such components using Base Metal Electrodes such as copper, a significant reduction of their sintering temperature is required. The aim of this work is first to study the effects of glass phases additions and secondly the stoichiometry influence on the sintering temperature of BZT and BZN. It is shown for example, that our materials can be sintered in air at a temperature lowered by 450C when sintering agents (B2O3 with LiF) are combined with a slight non-stoichiometry. The sintered samples are characterised in terms of final density, microstructure and phase content and it was underlined that such modifications (additions and stoichiometry) does not affect the dielectric properties.  相似文献   

13.
在CaO-SrO-Li2O-Sm2O3-Nd2O3-TiO2(简称CSLLT)陶瓷中加入BaCu(B2O5)(简称BCB),研究了BCB对CSLLT陶瓷的烧结特性和介电性能的影响。结果表明:随BCB的添加,CSLLT陶瓷的烧结温度逐渐下降,并且具有高介电常数。其中,添加10?B后的CSLLT陶瓷其烧结温度从1 300℃显著下降到1 050℃,且在微波频率下具有如下介电性能:ε=77.3、Qf=4 735 GHz;τf=-48.1×10-6/℃(1 MHz)。  相似文献   

14.
SrLnAlO4 (Ln=Nd and Sm) ceramics with K2NiF4 structure were prepared by a solid state reaction approach, and their microwave dielectric characteristics were evaluated together with the microstructures. The single phase dense SrNdAlO4 and SrSmAlO4 ceramics were obtained by sintering at 1450–1475°C and 1475–1500°C, respectively, and the good microwave dielectric characteristics were achieved: (1) = 17.8, Q · f = 25,700 GHz, f = –9 ppm/°C for SrNdAlO4; and (2) = 18.8, Q · f = 54,880 GHz, f = 2 ppm/°C for SrSmAlO4 dense ceramics. The Qf value significantly increased with increasing sintering temperature.  相似文献   

15.
The study of the dielectric properties of the stoichiometric Titanium doped Sr0.255La0.03Ba0.7Nb2O6 ceramics prepared according to the formula Sr0.225La0.03Ba0.7Nb2–yTiyO6–y/2 is reported. A single phase compound is observed for low Ti content (y<0.1) in the XRD spectra, being isostructural with the SBN phase. For high Ti concentrations (y<0.1), the XRD patterns show, besides the SBN phase reflections, several small peaks associated with an additional phase present in the ceramics. A possible liquid phase sintering is analyzed. Strongly broadened dielectric curves are obtained in dielectric measurements, where the transition temperature decreases with the Titanium content. The diffuse phase transition coefficients are calculated, corroborating that Titanium increases the diffuse character of the transition in the monophasic region.  相似文献   

16.
张奎  刘心宇  骆颖  杨华斌 《电工材料》2006,(2):21-23,42
研究了添加不同质量分数Al2O3的掺杂Nb的BaTiO3陶瓷材料。测量了烧结条件为1 300~1 350℃的陶瓷材料试样的室温电阻、R_T曲线、电阻温度系数及开关温度。在实验的基础上,分析讨论了不同含量的非晶态Al2O3与α_Al2O3对PTCR陶瓷电特性的影响。结果表明,随着Al2O3添加量的增加,材料的烧结温度降低,晶粒均匀,但材料的电特性变弱。  相似文献   

17.
采用微波快速烧结法制备了La掺杂CaCu3Ti4O12致密陶瓷,研究了其结构、介电和压敏性能。所有Ca1-3x/2LaxCu3Ti4O12陶瓷均形成了CCTO晶相,但是La含量低于0.10时存在CuO第二相。随着La含量增加,Ca1-3x/2LaxCu3Ti4O12陶瓷介电常数随频率和温度变化越来越小;压敏电压逐渐增大,非线性系数也明显改善。其中La含量x=0.15时,Ca1-3x/2LaxCu3Ti4O12陶瓷具有良好的压敏性能:压敏电场强度为5.25 kV/cm,非线性系数为26.3。  相似文献   

18.
Pb(Yb1/2Nb1/2)O3-PbTiO3 ceramics at the morphotropic phase boundary (50:50) were sintered by conventional and reactive methods to 95% theoretical density and grain sizes <10 m. Excess PbO, added to enhance the densification, resulted in PbO-based non-ferroelectric phases that degraded the electrical properties. Volatilization of excess PbO by annealing the samples after sintering resulted in dense, perovskite samples and excellent electrical properties. The best electrical properties, obtained via reactive sintering, were a remanent polarization, P r, of 0.36 C/m2, a maximum dielectric constant of 31,000 (at the T c = 371°C and 1 kHz), a piezoelectric charge coefficient, d 33, of 508 pC/N, and an electromechanical coupling coefficient, k 33, of 0.61.  相似文献   

19.
Pure aluminum nitride (AIN) has been successfully sintered to highly translucent form by microwave sintering at 1850°C with a dwelling time of 30–60 minutes. The results showed that the sintering temperature should be at least 1850°C or higher to get reasonable translucency in the AIN sample by the microwave sintering process. On the other hand, the conventional sintering method requires much longer sintering time to obtain a translucent AIN ceramics.  相似文献   

20.
随着现代移动通信的飞速发展,高介电常数微波介质陶瓷得到了极大的发展,并广泛应用于微波谐振器、滤波器、介质基板、移相器等微波元器件。本文综述了高介微波陶瓷之一的新型钨青铜型高介微波陶瓷近几十年来的研究进展,并展望了其发展趋势。  相似文献   

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