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1.
Fidel Guerrero Harvey Amori´n Jorge Portelles Jesu´s M. Siqueiros Sara Aguilera 《Journal of Electroceramics》1999,3(1):85-89
The effect of Lanthanum cation doping in the diffuse phase transition of the Sr0.3–3y/2LayBa0.7Nb2O6 ceramic system is studied for y=0.01, 0.03 and 0.05. For these compositions, the transition temperature T
c shifts towards higher values with increasing frequency and the temperature dependence of the electrical permittivity presents strongly broadened curves which suggest a non Curie-Weiss behavior near the transition temperature for temperatures far from T
c. The diffuse phase transition coefficient () was also determined and its values lead us to conclude that the degree of disorder in the system increases with the presence of the Lanthanum cation. This result is corroborated by calorimetric measurements, where an increase in entropy with the Lanthanum concentration is also found. 相似文献
2.
Fidel Guerrero Harvey Amori´n Jorge J. Portelles Abel Fundora Jesu´s M. Siqueiros Gustavo A. Hirata Sara Aguilera 《Journal of Electroceramics》1999,3(4):377-385
A study of the dielectric properties of the Lanthanum doped Sr0.3Ba0.7Nb2O6 (SBN30) ceramic according to the stoichiometric formulation Sr0.3–3y/2LayBa0.7Nb2O6 with y = 0.01, 0.03 and 0.05, and the influence of the sintering conditions is reported. The XRD shows single phase compounds for Sr0.285La0.01Ba0.7Nb2O6 (LSBN1) and Sr0.225La0.03Ba0.7Nb2O6 (LSBN3) ceramics, both samples having similar microstructure, densification and dielectric properties. The density increases linearly with ln t, where t is the sintering time, and the values of the maximum ferroelectric peaks of the permittivity increase steadily with t. Using the Bruggeman model to estimate the theoretical permittivity, it is concluded that the magnitude of the experimental permittivity peaks are mainly affected by the volume fraction of porosity of the samples. In this study we also establish that pore diffusion mechanisms behave according to the Ginstling-Brownshtein equation. For the Sr0.225La0.05Ba0.7Nb2O6 (LSBN5) sample, XRD analysis reveals the presence of isostructural compounds of the intermediate phases BaNb2O6 and SrNb2O6, and the dielectric properties start to deteriorate. This fact indicates the existence of a solubility limit of Lanthanum ions in the SBN solid solution. 相似文献
3.
P. K. Patro R. D. Deshmukh A. R. Kulkarni C. S. Harendranath 《Journal of Electroceramics》2004,13(1-3):479-485
Sr0.5Ba0.5Nb2O6 (SBN50) has been synthesized by coprecipitation method using Sr(NO3)2, Ba(NO3)2 and Nb-oxalate as precursors and ammonium hydroxide as precipitant. Calcination at 1150C resulted in pure SBN50 phase (XRD) and nano powder with size varying between 100–250 nm (TEM). The average grain size (SEM) in the sintered pellets ranged from 2.5 to 5 m as the sintering temperature varied from 1250 to 1350C. The maximum sintered density was observed to be 93% of th. The plot of dielectric constant vs. temperature clearly showed a shift of dielectric maxima (max) with frequency, indicating the relaxor nature of SBN50. The room temperature dielectric constant (RT > 2300) observed for all these samples is higher compared to the earlier reported values (RT 1500). The Tc (for 1 KHz) varied from 47–60C depending on the sintering conditions. The hystersis loops were recorded at various temperatures. The maximum saturation polarization for the unpoled pellets was found to be 2.3 C/cm2 when sintered at 1350C. The improvement in dielectric and ferroelectric behavior is attributed to the enhanced homogeneity attained by the coprecipitation synthesis route used in the present study. Correlations between microstructure (sintering conditions) and dielectric behavior is explored. 相似文献
4.
Ba1?x Sr x TiO3 (BST) thin films were prepared on the substrate of Pt/Ti/SiO2/Si by using novel sol–gel process through carbonates. The surface morphology and domain contrast of the films were investigated by atomic force microscopy (AFM), and the domain structures of the BST film were observed when AFM were operated in piezoelectric force microscopic (PFM) analysis and in the friction mode (FFM). The ferroelectric properties of the films were also investigated. It is shown that BST films obtained by the new sol–gel process through carbonates exhibit good properties. 相似文献
5.
P. P. Bardapurkar N. P. Barde D. P. Thakur K. M. Jadhav G. K. Bichile 《Journal of Electroceramics》2012,29(1):62-70
Growing interest in developing new materials for device applications led to study of ferroelectric oxides in a wide range and variety of compositions. In the present work, polycrystalline samples of lead barium strontium titanate (Pb1-xBa0.5xSr0.5xTiO3) solid solution system have been synthesized. Phase formation studies and crystal structure analysis were carried out by X ray diffractometry at room temperature, which suggested formation of single phase compound with tetragonal structure up to x?=?0.8 and cubic structure for x?=?1.0. The XRD pattern has been analyzed by employing Rietveld method. The phase transition in the system was confirmed by Differential Scanning Calorimetry (DSC). Samples with 0.0????x????0.8 are in ferroelectric state whereas with x?=?1.0 is found to be in paraelectric state at room temperature. Co-substitution of Ba2+ and Sr2+ into lead titanate shows reduction in anisotropy as well as porosity. The dielectric studies of the system as a function of temperature and frequency were carried out in the range 323?K to 773?K and 100?Hz to 1?MHz respectively. Variation of dielectric constant and loss tangent with temperature shows peaking effect near Curie temperature. Frequency dependant dielectric studies clearly show that the dielectric constant and loss tangent decrease exponentially with increased frequency. 相似文献
6.
Martin Sòaard Peter V. Hendriksen Finn W. Poulsen Mogens Mogensen 《Journal of Electroceramics》2004,13(1-3):811-816
The perovskites (La0.85Sr0.15)0.98CoO3 – and (La0.85Sr0.15)1.00CoO3 – have been investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical conductivity relaxation (ECR). This system was chosen in order to investigate the influence of cation vacancies on the transport properties in the materials. From ECR-measurements it is concluded that no difference in the chemical diffusion coefficient for oxide ions between the two samples can be found. The activation energy for the chemical diffusion coefficient has been found to be 107 ± 5 kJ mol– 1. However, the surface exchange coefficient differs between the two samples. The Co-rich sample has a significantly higher surface exchange coefficient than the A/B-stoichiometric sample. For both samples the surface exchange coefficient was almost independent of the temperature. At all temperatures the Co-rich sample had a significantly higher electrical conductivity. The difference in electrical conductivity between the two samples diminished when going to higher temperatures. Both materials can be assigned to a single phase hexagonal perovskite. An annealed sample of (La0.85Sr0.15)0.98CoO3 – did however contain an unidentified secondary phase on the surface. 相似文献
7.
A wide range of Ca-doped (Ba0.7Sr0.3)TiO3 (BST) thin films (from 0 to 20 mol%) have been prepared on Pt/Ti/SiO2/Si (100) substrates by sol–gel technique. The structural and dielectric properties of BST thin films were investigated as a function of Ca dopant concentration. The results showed that the microstructure and dielectric properties of the BST films were strongly dependent on the Ca contents. With the Ca dopant concentration increasing, the grain size, dielectric constant and dielectric loss of the BST thin films decreased. As the content of Ca dopant reaches 10 mol%, the dielectric constant, dielectric loss, tunability, the value of FOM and the leakage current density are 281, 0.0136, 16.7%, 12.3 and 5.5?×?10?6 A/cm2, respectively. 相似文献
8.
Relaxor ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) thin films with [001] preferential orientation were deposited on platinized silicon wafers by a sol–gel method, in which a PbO seeding layer was involved. The influences of annealing temperature on the crystal phase, microstructure, and electrical properties of the PMN–PT films were investigated. Pyrochlore-free perovskite PMN–PT films could be formed on PbO-seeded Pt(111)/Ti/SiO2/Si wafers at 800 °C, which was also the optimal annealing temperature for endowing the film with the best ferroelectric and dielectric properties. The enhanced properties were attributed to the improved crystallinity and microstructure. The leakage behaviors of the PMN–PT films annealed at different temperatures were also measured and discussed. 相似文献
9.
In-Sun Cho Jeong Seop Lee Shin-Tae Bae Jeong-Ryeol Kim Kug Sun Hong 《Journal of Electroceramics》2009,23(2-4):154-158
BaNb2P2O11 and Ba3Nb2P4O18 compounds with corner-sharing NbO6 octahedra and PO4 tetrahedra were prepared by a conventional solid-state reaction method. The crystal structure and microstructure were investigated by X-ray powder diffraction and field emission scanning electron microscope, respectively. The microwave dielectric properties were measured using a network analyzer. Both ceramics were sintered at a relatively low temperature of 1150 °C and had a relative density of ~96%. Compared to Ba3Nb2P4O18, BaNb2P2O11 had a higher permittivity of 31.7. However, the quality factor of BaNb2P2O11, was smaller than Ba3Nb2P4O18. Furthermore, the effect of the crystal structure on the microwave dielectric properties was investigated. 相似文献
10.
The crystal structure and the properties of a new microwave dielectric ceramics x SrTiO3–(1???x)Sr(Mg1/3Nb2/3)O3 have been investigated. With x?=?0.025, The new microwave dielectric ceramic achieves the dielectric properties of a dielectric constant ? r ~27.8, a Q?×?f value ~26,800, and a τ f value ~7.4 ppm/°C. When the SrWO4 is added, the sintering temperature of x SrTiO3–(1???x)Sr(Mg1/3Nb2/3)O3 ceramics will fall to 1350 °C, and its Q?×?f value can be improved further and the τ f value becomes smaller. When the SrWO4 is added by 0.07 mol, the specimen acquires the following microwave properties: a dielectric constant ? r ~30.3, a Q?×?f value ~29,500, and a τ f value of approximately ?0.4 ppm/°C. 相似文献
11.
The Ba2TiSi2O8 glass-ceramics were prepared by sol–gel process using barium acetate, titanium butoxide, tetraethoxyorthosilicate and boric acid as raw materials. Because of the existence of glass and sintering additive, the Ba2TiSi2O8 glass-ceramics can be sintered at 880 °C in air. The structure of sintered sample was characterized by means of XRD and SEM. XRD patterns showed that fresnoite Ba2TiSi2O8 is the dominant crystalline phase in the sintered samples. SEM images indicated that the shape of Ba2TiSi2O8 grains varied with the molar ratio of ([Ba(Ac)2/Ti(OBun)4/Si(OEt)4]). With an increase of Si(OEt)4 content, the length/diameter ratio of Ba2TiSi2O8 grains decreases. The Ba2TiSi2O8 glass-ceramics studied in this work have ?r in the range of 6–12 (100 MHz) and demonstrate very low dielectric losses (tanδ <2?×?10?3, 100 MHz). The experimental results suggested that the Ba2TiSi2O8 glass-ceramics could be used as dielectric materials for low temperature co-fired ceramics (LTCC) process. 相似文献
12.
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
13.
Structure and electrical properties of (1???x)Pb(Zn0.2Ni0.8)1/3Nb2/3O3–xPbTiO3 ceramics with x?=?0.24–0.38 were examined in detail. X-ray diffraction measurements reveal that all samples are in pure perovskite phase, and most of them lie within the morphotropic phase boundary (MPB) region. The dielectric behaviors of all compositions are characterized with diffuse phase transition and frequency dispersion. The variable power law and the Vogel–Fulcher relation have been used to describe such dielectric behaviors. The highest dielectric constant and the largest piezoelectric coefficient are simultaneously observed when x?=?0.30. The variation of the ferroelectric property with PT content is also discussed. 相似文献
14.
LaCoO3–/La2(Zr,Y)2O7-based composites were designed in view of three main properties: electrical conductivity, thermal expansion and resistance to thermal cycling. Composition and processing conditions were investigated on the basis of an experimental plan according to the Taguchi method. The phase distribution was estimated from image analysis and related to electrical and thermo-mechanical behavior. Results indicate that an homogeneous and fine grained phase distribution is essential in order to obtain materials with the desired thermal expansion, electrical properties and thermomechanical properties. 相似文献
15.
N. Bensemma G. Trefalt S. Glinšek M. Kosec K. Taïbi M. Abbaci 《Journal of Electroceramics》2013,30(4):206-212
Lead-free (1?x) BaTiO3 –x BaMg1/3Nb2/3O3 ceramics with x?=?0.03, 0.04, 0.05 and 0.06 were prepared by solid-state synthesis. The effects of the Ba(Mg1/3Nb2/3)O3 addition on the phase composition, dielectric and ferroelectric properties, as well as the electromechanical response of the classic ferroelectric BaTiO3 were investigated. The room-temperature X-ray diffraction analyses of all the ceramics revealed a perovskite phase after sintering at 1300 °C with a composition-dependent symmetry. The samples with a lower concentration of Ba(Mg1/3Nb2/3)O3, i.e., x?=?0.03 and 0.04, were tetragonal, while the samples with x?=?0.05 and 0.06 were found to be cubic. The result is in agreement with the dielectric, ferroelectric and electromechanical properties. With x increasing from 0.03 to 0.06 the temperature of the diffused maximum of the dielectric permittivity decreased from 348 K to 265 K. All the ceramics showed a large electromechanical response: the calculated room-temperature electrostrictive coefficient M 33 of the sample with x?=?0.06 was 1.4 · 10?16?m2/V2, which is comparable to the value measured for Pb(Mg1/3Nb2/3)O3 ceramics. 相似文献
16.
We report a systematic study of the (1???x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 (PSN–PT) solid solution in the form of ceramics with compositions at or near the morphotropic phase boundary (MPB) region (0.35?≤?x?≤?0.50). The PSN–PT ceramics have been synthesized by an improved two-step wolframite precursor method. The synthetic process has been optimized in terms of calcining and sintering conditions. Both dielectric permittivity measurements and differential scanning calorimetry (DSC) show a clear peak at T C, at which the transition from the paraelectric to ferroelectric phase takes place. Interestingly, the solid solution of the MPB compositions displays a T C?>?200 °C, i.e. higher than the T C of the Pb(Mg1/3Nb2/3)O3–PbTiO3 and Pb(Zn1/3Nb2/3)O3–PbTiO3 solid solutions, making the PSN–PT system very promising piezoelectric and ferroelectric materials for high-temperature applications. A dielectric maximum as high as 50,000 is obtained for the 0.65PSN–0.35PT ceramic with losses smaller than 0.05. The values of the remnant polarization and the strain level of the PSN–PT ceramics are comparable to those of the PZT ceramics. 相似文献
17.
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
18.
Ba(Nd0.8Sm0.2)2Ti4O12 ceramics prepared by conventional solid-state sintering have a dielectric constant of about 80 and a nearly zero temperature coefficient of resonant frequency; however, the sintering temperature is above 1350_C. Doping with B2O3 (up to 5 wt%) promotes the densification and dielectric properties of BNST ceramics. It is found that coating BNST powder with thin B2O3 layer of about 180 nm reduces the sintering temperature to below 1020_C. The effects of B2O3 nano-coating on the dielectric microwave properties and the microstructures of BNST ceramics are investigated. Ninety-six percent of theoretical densities is obtained for specimens coated with 2 wt% B2O3 sintered at 960_C and the samples exhibit significant (002) preferred orientation and columnar structure. 相似文献
19.
Jin Wang Zhenxing Yue Jing Yan Zhilun Gui Longtu Li 《Journal of Electroceramics》2008,21(1-4):116-119
The ZnO–xV2O5 substituted ZnNb2O6 ceramics with chemical formula Zn(Nb0.9V x )2O5.5+5x (0?<?x?≤?0.10) were prepared by solid-state reaction route. The densities, microstructures and microwave dielectric properties were investigated according to the different substitution amount of V2O5 and sintering temperature. A small amount of substitution of ZnO–xV2O5 was effective to lower sintering temperature of ZnNb2O6 ceramics from 1,150 °C to 900 °C. The V2O5 substitution led to growth of rod-like grains with the help of liquid phase formed from ZnO and V2O5. The dielectric properties depended largely on the amount of V2O5 substitution and sintering temperature. The dense ceramics with x?=?0.05 were obtained at 950 °C, which had excellent dielectric properties: ?r?=?24, Q?×?f?=?72,800 GHz and τf?=??63.5 ppm/°C. The interface analysis for cofired multilayer composites composed of the present LTCC and metal Ag demonstrated good co-firing chemical compatibility at co-sintering temperature. 相似文献
20.
In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, Pb(Mn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr0.50Ti0.50)O3 (abbreviated as PMN-PNN-PZT) ceramics were fabricated using Li2CO3 and Na2CO3 as sintering aids, and their piezoelectric and dielectric characteristics were investigated according to the amount of MnO2 addition. At the 0.2 wt% MnO2 doped specimen sintered at 900 °C, density and mechanical quality factor (Q m) showed the maximum values of 7.81[g/cm3]and 1186, respectively. And also, at 0.1 wt% MnO2 doped specimen, electromechanical coupling factor (k p), piezoelectric constant (d 33) of specimen showed the maximum values of 0.608 and 377[pC/N], respectively. Dielectric constant (? r) slightly decreased with increasing MnO2. Taking into consideration the density of 7.81[g/cm3], electromechanical coupling factor (k p)of 0.597 the mechanical quality factor (Q m) of 1,186, and piezoelectric constant (d 33) of 356[pC/N], it could be concluded that 0.2 wt% MnO2 doped composition ceramics sintered at 900 °C was best for low loss and low temperature sintering multilayer piezoelectric actuator application. 相似文献