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1.
Materials in the (Na0.5Bi0.5)TiO3–SrTiO3 system are of interest for use as lead-free piezoelectric actuators due to high electric-field induced strains. Piezoelectric properties may be further improved by growing single crystals but as yet work on single crystal growth in this system is limited. In the present work, single crystals of composition 0.75 (Na0.5Bi0.5)TiO3?0.25 SrTiO3 were grown by solid state crystal growth (SSCG) on [001] SrTiO3 seed crystals and the dependence of crystal growth distance and matrix grain growth on sintering temperature investigated. Electron backscattered diffraction and X-ray diffraction analysis show that the single crystals grow epitaxially on the seed crystals. Energy dispersive spectroscopy indicates that the grown crystals are slightly Na-deficient, while X-ray photoelectron spectroscopy indicates the presence of oxygen vacancies. Single crystal growth distance, mean matrix grain size and grain size distribution as a function of sintering temperature and time are presented. Increasing the sintering temperature increases both single crystal and matrix grain growth rates. The optimum single crystal growth temperature is found to be 1250°C. The effect of sintering temperature on the single crystal and matrix grain growth behavior is explained using the mixed control mechanism of microstructural evolution. 相似文献
2.
Trang An Duong Hyoung-Su Han Young-Hwan Hong Young-Seok Park Hoang Thien Khoi Nguyen Thi Hinh Dinh Jae-Shin Lee 《Journal of Electroceramics》2018,41(1-4):73-79
This study investigated the microstructure, crystal structure, and electrical properties of (1???x)Bi1/2Na1/2TiO3–xSrTiO3 (BNST100x; x?=?0.20, 0.22, 0.24, 0.26, 0.28, and 0.30) lead?free piezoceramics. The average grain size of BNST100x ceramics decreased with increasing SrTiO3 content. A phase transition from nonergodic relaxor (NER) to ergodic relaxor (ER) was observed at x?=?0.26, and the highest unipolar strain under 4 kV/mm electric field, of 0.25% (d33*?≈?620 pm/V), was obtained at x?=?0.28. We found that the BNST26 and BNST28 compositions yielded the competitive advantage of larger strain values under lower operating fields compared with other BNT–based lead–free piezoelectric ceramics. Therefore, we regard these ceramics as promising candidates for actuator applications. 相似文献
3.
Lead-free perovskite (0.995–x)(K0.5Na0.5)NbO3–x(Bi0.5Li0.5)ZrO3–0.005BiAlO3 ternary piezoelectric ceramics were projected and prepared by a conventional solid-state method. A research was conducted on the effects of (Bi0.5Li0.5)ZrO3 content on the structure and piezoelectric properties of the ceramics. By combining the X-ray diffraction patterns with the temperature dependence of dielectric properties, a rhombohedral–orthorhombic–tetragonal phase coexistence was identified for the ceramics with 0.02 ≤ x ≤ 0.025, and a rhombohedral–tetragonal phase boundary was determined in the composition x = 0.03. Upon further increasing the (Bi0.5Li0.5)ZrO3 content, the rhombohedral–tetragonal phase boundary transformed to a single rhombohedral structure with x ≥ 0.035. An obviously improved piezoelectric activity was obtained for the ceramics with compositions in and around the rhombohedral–tetragonal phase boundary, among which the composition x = 0.025 exhibited the maximum values of piezoelectric constant d 33, and planar and thickness electromechanical coupling coefficients (k p and k t), of 252 pC/N, 0.366, and 0.466, respectively. In addition, the ceramic with x = 0.025 was found to possess a relatively high Curie temperature of 368 °C, suggesting it may have a prospect for applications at elevated ambient temperatures. 相似文献
4.
Chang-Heon Lee Hyoung-Su Han Seong Hyun Kim Thi Hinh Dinh Chang Won Ahn Jae-Shin Lee 《Journal of Electroceramics》2018,41(1-4):43-49
This study examined the microstructures, crystal structures, and electrical properties of 0.01 mol CuO–added (1–x)(Bi1/2Na1/2)TiO3–xSrTiO3–2BiFeO3 (BNST100x–2BF, x?=?0.20 ~ 0.28) ceramics synthesized at two different sintering temperatures. The sintering temperature of the BNST100x–2BF ceramics could be decreased from 1175 °C to 1000 °C by adding a 0.01 mol CuO excess. Low–temperature sintering led to a decrease in average grain size. The dielectrics, polarization hysteresis (P–E), switching current, and electric–field induced strain (S–E) curves changed with increasing SrTiO3 content and decreasing sintering temperature. Interestingly, the highest reduction ratio of d33* was calculated to be somewhere in between the high–temperature sintered and low–temperature sintered BNST26–2BF ceramics. These results were attributed to the difference in the stabilized relaxor state and closely related to the electric field–induced reversible phase transition from the relaxor and ferroelectrics. 相似文献
5.
MgO (0–2.0 vol%) added Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT-0.5BCT) ceramics have been prepared by the conventional solid-state reaction method. The effects of MgO powder on the phase formation, densification, dielectric, piezoelectric and mechanical properties (flexural strength, hardness) of the BZT-0.5BCT ceramics have been studied systematically. The synthesized powder could be densified to 97 % of true density at a temperature of 1350 °C. The MgO addition also provided materials with better mechanical properties. The most interesting aspect of MgO added samples is their relative permittivity vs. temperature response. MgO additions effectively suppress the relative permittivity around phase transition temperature. The aging rate of d33 observed for BZT-0.5BCT is 14 %/decade. MgO addition reduces the ageing rate and for 1 vol% MgO added, BZT-0.5BCT shows aging rate of 3 %/decade. BZT-0.5BCT/MgO ceramics possesses good mechanical properties viz., flexural strength 93 MPa, which is almost 25 % higher than that of monolithic BZT-0.5BCT (73 MPa). 相似文献
6.
BaO ⋅ Nd2O3 ⋅ 4TiO2—based ceramics were prepared by the mixed oxide route. Specimens were sintered at temperatures in the range 1200–1450∘C. 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 100∘C. 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
7.
Single-phase perovskite structure 0.8BiFeO3–0.2SrTiO3 ceramics were synthesized by a modified sol-gel method. According to the scanning electron microscopy results, the grain sizes of as-prepared samples increased obviously as the annealing temperature rose. Compared with pure BiFeO3, superior multiferroic and dielectric properties were obtained i.e. remnant magnetization Mr?=?0.10 emu/g with a maximum magnetic field of 50 kOe and maximum polarization Pmax?=?8.738 μC/cm2 with an applied electric field of 50 kV/cm. Furthermore, the volcano-shape evolution of diffraction peaks and maximum magnetization with increasing sintering temperature indicate that appropriate annealing temperature has a remarkable influence on the enhancement of the multiferroic properties and dielectric performance of 0.8BiFeO3–0.2SrTiO3 ceramics. The annealing temperature that yields the most favorable multiferroic properties for the 0.8BiFeO3–0.2SrTiO3 solid solution ceramic is somewhere close to 1300 K. 相似文献
8.
Fazli Akram Rizwan Ahmed Malik Salman Ali Khan Ali Hussain Soonil Lee Myang-Hwan Lee Choi Hai In Tae-Kwon Song Won-Jeong Kim Yeon Soo Sung Myong-Ho Kim 《Journal of Electroceramics》2018,41(1-4):93-98
In the present work, composition dependent crystal structure, ferroelectric, piezoelectric, and temperature dependent dielectric properties of the BiGaO3-modified (1–x)(0.65Bi1.05FeO3–0.35BaTiO3) (BFBT35–xBG, where x?=?0.00–0.03) lead-free ceramics were systematically investigated by solid-state reaction method, followed by water quenching process. The substitution of BG successfully diffuses into the lattice of the BFBT ceramics, without changing the pseudo-cubic structure of the samples. The scanning electron microscopy (SEM) results revealed that the average grain size was increased with BG-content in BFBT system. The BFBT–xBG ceramics showed a maximum in permittivity (?max) at temperatures (Tmax) above 500 °C in the compositional range of 0.00?≤?x?≤?0.03. The electro-strain is measured to be 0.125% (d*33 ~ 250 pm/V) under unipolar fields (5 kV/mm) for BFBT–0.01BG ceramics. The same composition (x?=?0.01), large static piezoelectric constant (d33 ~ 165 pC/N) and electromechanical coupling factor (kp ~ 25%) were obtained. The above investigated characterizations suggests that BFBT–BG material is favorable for piezoelectric and high temperature applications. 相似文献
9.
C. M. Raghavan J. W. Kim S. S. Kim J. -W. Kim T. K. Song 《Journal of Electroceramics》2016,36(1-4):76-81
Aurivillius type five-layered V-doped Bi6Fe2(Ti3-xVx)O18+δ (x = 0.00, 0.03, 0.06, and 0.09) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. All the thin films were crystallized in Aurivillius structures, which have been confirmed by using X-ray diffraction and Raman spectroscopy studies. On comparing the thin films, the Bi6Fe2(Ti2.94V0.06)O18+δ thin film showed the most enhanced electrical and multiferroic properties, with a leakage current density value about four orders of magnitude lower than that of the Bi6Fe2Ti3O18 thin film, for example. All of these thin films showed anti-ferromagnetic hysteresis loops at room temperature. The significant decrease in the concentration of oxygen vacancies and the formation of a stable structure caused by doping with the donor V5+-ion are related to the improved properties in the V-doped Bi6Fe2(Ti3-xVx)O18+δ thin films. 相似文献
10.
Adnan Maqbool Rizwan Ahmed Malik Ali Hussain Fazli Akram Muhammad Asif Rafiq Mohsin Saleem Fazal Ahmad Khalid Tae-Kwon Song Won-Jeong Kim Myong-Ho Kim 《Journal of Electroceramics》2018,41(1-4):99-104
Heat treatment of ceramics is an important process to tailor the fine electromechanical properties. To explore the criteria for optimized heat treatment in a perovskite structure of (1–x)Bi1.05FeO3–xBaTiO3 (BF–BT100x) system, the structural phase relation, ferroelectric and piezoelectric response of BF–BT36 and BF–BT40 ceramics prepared by furnace cooling (FC) and quenching process were investigated. The X-ray diffraction examination showed single pseudocubic perovskite structure for all the ceramics. The homogenous microstructure was obtained for all ceramics with relatively large grain size in the furnace cooled samples. Well saturated ferroelectric hysteresis loops and enhanced piezoelectric constant (d33?=?97 pC/N) were achieved by quenching process. Dielectric curve of BF–BT36 showed large dielectric constant at its Curie temperature, however, BF–BT40 showed diffused relaxor-like dielectric anomalies. Quenched BF–BT36 samples showed typical butterfly like field induced strain curves, however negative strain decreased in BF–BT40 ceramics. From these investigated study, it is observed that BF–BT ceramics are very sensitive to the heat treatment process (furnace cooling and quenching) on the dielectric, electromechanical properties. 相似文献
11.
Partial electronic conductivity and chemical diffusivity of Li have been measured on the system of Li3xLa2/3–xTiO3 (LLT) with x = 0.13, a prospective Li+ electrolyte, against oxygen activity in the range of 10–22 < aO2 < 0.21 at 557, 610 and 663C, respectively by an ion-blocking polarization technique. It is found that the electronic conductivity of LLT, which in air is essentially an ionic conductor, varies as aO2–1/4 to render it mixed-conductive in reducing atmospheres, say, in aO2 < 10–12. The chemical diffusivity of component Li also increases from a value of the order of 10–8 cm2/s in air atmosphere up to a maximum on the order of 10–3 cm2/s as the electronic conductivity increases with decreasing oxygen activity. This is attributed to the variation of the electronic transference number and the thermodynamic factor with oxygen activity. The latter has been evaluated to be on the order of 10–103. 相似文献
12.
Chunhua Zhao Zhongbing Wang Shouming Wang Pinghua Yang Chusheng Chen 《Journal of Electroceramics》2008,20(2):113-117
The composites made of spinel-structured (Ni,Mn)3O4 and perovskite-structured La(Mn,Ni)O3 were investigated for potential application as negative temperature coefficient (NTC) thermistor. The composites were prepared
using the standard ceramic route. The electrical resistivity of the composite at 25°C was found to decrease by one to two
orders of magnitude depending the amount of the low-resistivity perovskite phase, while the thermal constant determining the
temperature sensitivity of the NTC thermistor was still reasonably large in the range of 4,000 to 3,000 K, and the resistivity
drift after annealing at 150°C for 1,000 h in air was relatively small (∼1.2%). The general effective media model was adopted
to fit the electrical resistivity data of the composites, giving a value of 0.37 for the percolation volume fraction of the
perovskite phase. This work demonstrates that it is possible to tune the electrical resistivity and thermal constant of the
spinel-structured oxide through making composite with low-resistivity perovskite-structured oxide. 相似文献
13.
The effect of mechanical loading on the tuning performance of a tunable Thin Film Bulk Acoustic Wave Resonator (TFBAR) based
on a Ba0.3Sr0.7TiO3 (BST) thin film has been investigated experimentally and theoretically. A membrane-type TFBAR was fabricated by means of
micromachining. The mechanical load on the device was increased stepwise by evaporating SiO2 on the backside of the membrane. The device was electrically characterized after each evaporation step and the results were
compared to those obtained from modeling. The device with the smallest mechanical load exhibited a tuning of − 2.4% and − 0.6%
for the resonance and antiresonance frequencies at a dc electric field of 615 kV/cm, respectively. With increasing mechanical
load a decrease in the tuning performance was observed. This decrease was rather weak if the thickness of the mechanical load
was smaller or comparable to the thickness of the active BST film. If the thickness of the mechanical load was larger than
the thickness of the active BST layer, a significant reduction in the tuning performance was observed. The weaker tuning of
the antiresonance frequency was due to a reduced tuning of the sound velocity of the BST layer with increasing dc bias. The
resonance frequency showed a reduced tuning due to a decrease in the effective electromechanical coupling factor of the device
with increasing mechanical load. With the help of the modeling we could de-embed the intrinsic tuning performance of a single,
non-loaded BST thin film. We show that the tuning performance of the device with the smallest mechanical load we fabricated
is close to the intrinsic tuning characteristics of the BST layer. 相似文献
14.
Alena Movchikova Olga Malyshkina Gunnar Suchaneck Gerald Gerlach Ralf Steinhausen Hans Theo Langhammer Christoph Pientschke Horst Beige 《Journal of Electroceramics》2008,20(1):43-46
In this work, the thermal square wave method at single-frequency (TSWM) was applied to functionally graded BaTi1−x
Sn
x
O3 samples with a tin gradient of 0.075 ≤ x ≤ 0.15. The samples were fabricated by sintering of bi-, tri- and tetramorph green bodies. The polarization at the back side
with a higher tin content was in opposite direction to the polarization of the surface with a lower tin content. This was
attributed to the appearance of a space charge layer. The determined depth profiles of the pyroelectric coefficient illustrate
the appearance of a nearly constant polarization in the region of lower tin concentration of tri- and tetramorph samples.
The pyroelectric coefficient profiles were in good agreement with the averaged over sample thickness pyroelectric coefficient
obtained separately by the quasistatic method. 相似文献
15.
Strontium-doped lanthanum ferrites (LSF) were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), 4-point D.C. electrical conductivity and bulk property measurements. The results were compared to those of previous studies as well as selected processing conditions. The investigation focused on effects of sintering temperature, time, atmosphere (air, O2 and N2) and composition of La1–xSrxFeO3– (x = 0.2–0.9), on the sintering behavior, microstructural development and electrical conductivity. An oxalate precipitation method was used to prepare lanthanum ferrite powders. Simultaneous thermogravimetric and differential thermal analysis (TGA/DTA) studies found calcination temperatures of 800 and 850^C were necessary to form single-phase crystalline powders, as determined by XRD. Specimens were sintered from 1300 to 1400^C with dwell times from
to 2 hrs. Results from SEM/EDS analysis showed the presence of a second phase in the samples fired in air or oxygen. The second phase was not detected by x-ray diffraction due to the small amount of material present. Samples fired in nitrogen had the lowest conductivity while those fired in oxygen had the highest. A composition of x = 0.5 resulted in the highest conductivity, 352 S/cm, at an operating temperature of 550C in air. High strontium additions (x = 0.9) lowered the linear shrinkage of LSF. 相似文献
16.
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 (25∘C) to 300∘C, 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
17.
Perovskite-type Cd-doped LaCoO3 materials were synthesized by a simple solution-based combustion process. The synthesized materials were characterized by
powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance (DR) in the UV-VIS, and magnetic property
measurements. The parent LaCoO3 compound showed spin-glass transition at low temperatures, and with progressive Cd doping, showed transition to paramagnetic
ordering. The changes in magnetic properties of the materials are correlated to the changes in structural features resulting
from the Rietveld structural refinement of the materials. 相似文献
18.
Cathodic material La1.0Sr1.0FeO4+δ for an intermediate temperature solid oxide fuel cell (IT-SOFC) was prepared via the glycine-nitrate process and characterized
by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). XRD results
showed that no reaction occurred between the La1.0Sr1.0FeO4+δ electrode and Sm0.2Ce0.8O1.9 (SDC) electrolyte at 1000 °C. SEM results showed that the electrode formed good contact with the SDC electrolyte after sintering
at 1000 °C for 2 h. The electrochemical properties of La1.0Sr1.0FeO4+δ were measured using electrochemical impedance spectroscopy (EIS) and steady state polarization measurement. At 700 °C, the
polarization resistance was about 3.90 Ωcm2, and the lowest polarization overpotential was 57 mV at a current density of 55 mA cm−2. 相似文献
19.
Nanoscale switching of the lamellar 90∘ domains ({a-a} domains) of PbTiO3 grains in the surface of sol-gel-derived PbTiO3/Pb(Zr0.58Ti0.42)O3/PbTiO3 thin films is studied by three-dimensional piezoresponse force microscopy. It is demonstrated that the lamellar domain pattern in the PbTiO3 grains can be rotated 90∘ in the plane of film by the electric field at the tip. It is found that the rotation of lamellar domain pattern involves transverse growth of the existing embedded a-a domain nucleus, whose domain walls are perpendicular to the surrounding ones. During the transverse growth, the existing 90∘ domains extend along length direction and penetrate into neighboring domain walls, while formation of new 90∘ domain walls was mediated by the nanoscale 45∘ tilted spike domains. 相似文献
20.
The article deals with construction of a simplified model of inhibition of nitric oxides formed in the combustors of the gas-turbine plants (GTPs) operating on natural gas. A combustor in which premixed, lean air–fuel mixtures are burnt is studied theoretically and experimentally. The research was carried out using a full-scale combustor that had parameters characteristic of modern GTPs. The article presents the results computed by the FlowVision software and the results of the experiments carried out on the test bench of the All-Russia Thermal Engineering Institute. The calculations and the tests were conducted under the following conditions: a flow rate of approximately 4.6 kg/s, a pressure to 450 kPa, an air temperature at the combustor inlet of approximately 400°C, the outlet temperature t3 ≤ 1200°C, and natural gas as the fuel. The comparison of the simulated parameters with the experimental results underlies the constructed correlation dependence of the experimental NOx emission on the calculated parameter of nonuniform fuel concentration at the premixing zone outlet. The postulate about a weak dependence of the emission of NOx formed upon combustion of a perfectly mixed air–fuel mixture—when the methane concentration in air is constant at any point of the air–fuel mixture, i.e., constant in the mixture bulk—on the pressure in the combustor has been experimentally proven. The correctness and the practicability of the stationary mathematical model of the mixing process used to assess the NOx emission by the calculated amount of the air–fuel mixture generated in the premixing zone has been validated. This eliminates some difficulties that arise in the course of calculation of combustion and formation of NOx. 相似文献