共查询到20条相似文献,搜索用时 46 毫秒
1.
N. Bensemma G. Rekhila N. Boutal K. Taïbi M. Trari 《Journal of Materials Science: Materials in Electronics》2016,27(7):6757-6765
The lead-free Ba(Ti0.96Mg0.013Nb0.026)O3 composition has been prepared by solid state reaction. The room temperature X-ray diffraction revealed a perovskite phase with a tetragonal symmetry. The complex dielectric permittivity measured on cooling from 470 to 150 K in the frequency range (102–106 Hz) indicated a ferroelectric behavior and exhibited a large electromechanical response. This ferroelectric perovskite showed photoelectrochemical properties with an optical gap of 2.90 eV, n-type conduction and a flat band potential of ?0.57 V SCE . As application, the oxide is successfully tested for the eosin oxidation under solar light. At pH ~ 6.3, 90 % of eosin (15 mg L?1) disappeared after 6 h of illumination for a catalyst dose of 2.5 g L?1. 相似文献
2.
Lead-free (Na0.5Bi0.5)0.88Ba0.12TiO3 ceramics have been prepared and studied by X-ray diffraction and by the complex dielectric response as a function of temperature,
frequency and a.c. field intensity. Relaxor-like dielectric behaviour were induced by barium Ba dopping to Na0.5Bi0.5TiO3. It was shown, that relaxor-like characteristics can be enhanced by the increase of the a.c. field intensity. A sharp increase
in the electric permittivity and dielectric loss on heating near 230 °C has been observed. This sharp increase in dielectric
responses indicates a transformation between classical and relaxor ferroelectric phases. The X-ray diffraction study shows
that this transformation corresponds to the first order phase transition from tetragonal to cubic. The use of (Na0.5Bi0.5)0.88Ba0.12TiO3 ceramics for device applications has been indicated. 相似文献
3.
Liang Fang Zhao Yang Hui Zhang Chunchun Li Xiyang Peng Changzheng Hu Dongjin Chu 《Journal of Materials Science: Materials in Electronics》2011,22(9):1208-1212
Polycrystalline samples of Ba4Ln2Fe2Ta8O30 (Ln = La and Nd) were prepared by a high temperature solid-state reaction technique. The formation, structure, dielectric
and ferroelectric properties of the compounds were studied. Both compounds are found to be paraelectrics with filled tetragonal
tungsten bronze (TB) structure at room temperature. Dielectric measurements revealed that the present ceramics have exceptional
temperature stability, a relatively small temperature coefficient of dielectric constant (τ
ε
) of −25 and −58 ppm/°C, with a high dielectric constant of 118 and 96 together with a low dielectric loss of 1.2 × 10−3 and 2.8 × 10−3 (at 1 MHz) for Ba4La2Fe2Ta8O30 and Ba4Nd2Fe2Ta8O30, respectively. The measured dielectric properties indicate that both materials are possible candidates for the fabrication
of discrete multilayer capacitors in microelectronic technology. 相似文献
4.
A. G. Pinheiro F. M. M. Pereira M. R. P. Santos H. H. B. Rocha A. S. B. Sombra 《Journal of Materials Science》2007,42(6):2112-2120
A study of the effect of the presence of BIT (Bi4Ti3O12) in the dielectric and optical properties of the CaCu3Ti4O12 (CCTO) is presented. The samples were prepared by the solid state procedure. Mechanical alloying followed by the solid state
procedure has been used successfully to produce powders of CaCu3Ti4O12 (CCTO) and BIT (Bi4Ti3O12) to be used in the composites. We also look at the effect of the grain size of the BIT and CCTO in the final properties of
the composite. The samples were studied using X-Ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopy.
We also did a study of the dielectric function K and dielectric loss of the samples.
The role played by the grain size of CCTO and BIT in the dielectric constant and structural properties of the substrates are
discussed. For frequencies below 10 MHz the K value presented by the CCTO100 sample is always higher than the K value presented by the BIT100 sample. At 100 Hz the value of K 1900 for the CCTO100 sample and 288 for the BIT100 sample. However for the composite sample one has an unexpected result.
The dielectric constant is higher for all the frequencies under study. At 100 Hz the value of the K is around 10.000 for the BIT10 sample. Which is more than one order bigger compared to the CCTO100 value for the same frequency.
Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These
composites are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile
phones for example), where the miniaturization of the devices is crucial. 相似文献
5.
Lead-free ferroelectric ceramics of (1−x) [0.88Na0.5Bi0.5TiO3-0.12K0.5Bi0.5TiO3]-x KNbO3(x = 0, 0.02, 0.04, and 0.06) were prepared by the conventional ceramic fabrication technique. The crystal structure, dielectric properties and P-E hysteresis loops were investigated. XRD data showed that all compositions could form pure perovskite structure. Temperature dependence of dielectric constant ε r and dissipation factor tanδ measurement between room temperature and 500∘C revealed that the compounds experience phase transitions that from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric in the range of x = 0–0.04. The frequency dependent dielectric constant showed these compounds were relaxor ferroelectric. At low frequency and high temperature, dielectric constant and dissipation factor increased sharply attributed to the superparaelectric clusters after the KNbO3 doped. 相似文献
6.
O. Yu. Kravchenko L. A. Reznichenko G. G. Gadzhiev L. A. Shilkina S. N. Kallaev O. N. Razumovskaya Z. M. Omarov S. I. Dudkina 《Inorganic Materials》2008,44(10):1135-1150
The structural, dielectric, and thermal properties of the Na0.875Li0.125NbO3 solid solution doped with strontium and other elements have been studied in wide temperature and frequency ranges. The material has been shown to undergo a sequence of phase transitions accompanied by anomalies in its structural, dielectric, and thermal properties. The observed low-frequency dispersion of its dielectric permittivity is attributed to the effect of electrical conductivity. 相似文献
7.
xBaTiO3 + (1 − x)Ni0.93Co0.02Cu0.05Fe2O4 (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering
technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain
size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to
15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency
range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would
be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation
magnetization (M
s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic
phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric
materials. 相似文献
8.
Kangning Wu Yuwei Huang Linlin Hou Zhuang Tang Jianying Li Shengtao Li 《Journal of Materials Science: Materials in Electronics》2018,29(6):4488-4494
Effects of dc bias on dielectric relaxations in CaCu3Ti4O12 ceramics were investigated via an improved dielectric spectroscopy. A new low-frequency dielectric relaxation, which was assigned to space charge polarization, was found shifting towards higher frequency with increasing bias voltage in the improved spectra. It was suggested that the Schottky barrier at grain boundary was lowered under dc bias resulting in higher possibility for carriers to migrate. Therefore, the relaxation time was decreased, which was in accordance with rightward shift of this relaxation under increased dc bias. In addition, dependence of the widely reported high-frequency relaxation (>?105 Hz) and middle-frequency relaxation (103–105 Hz) on bias voltage was also discussed. Permittivity contributed by either high-frequency or middle-frequency relaxation presented inverse dependence on dc bias. Discrepancy on barrier parameters was obtained assuming both of them physically correlated with the barrier at grain boundary. 相似文献
9.
Debesh Devadutta Mishra Yao Huang Na Duan Guolong Tan 《Journal of Materials Science: Materials in Electronics》2018,29(12):9854-9860
Methylene blue (MB) is a representative of a class of dyestuffs resistant to biodegradation. This paper presents a novel photocatalytic degradation of MB by La0.2Sr0.7Fe12O19 compound, which is a traditional permanent magnet and displays a large magnetic hysteresis (M–H) loop. The remnant magnetic moment and coercive field are determined to be 52 emu/g and 5876 Oe, respectively. UV–Visible optical spectroscopy reveals that La0.2Sr0.7Fe12O19 is simultaneously a semiconductor, whose direct and indirect band gap energies are determined to be 1.47 and 0.88 eV, respectively. The near infrared band gap makes it a good candidate to harvest sunlight for photocatalytic reaction or solar cell devices. This magnetic compound demonstrates excellent photocatalytic activity on degradation of MB under visible illumination. The colour of MB dispersion solution changes from deep blue to pale white and the absorbance decreases rapidly from 1.8 down to zero when the illumination duration extends to 6 h. Five absorption bands did not make any blue shifts along with the reaction time, suggesting a one-stepwise degradation process of MB, which makes La0.2Sr0.7Fe12O19 a unique magnetic catalyst and differs from TiO2 and other conventional catalysts. 相似文献
10.
Suhua Fan Fengqing Zhang Guitao Liu Qingbo Tian Luyi Zhu 《Journal of Materials Science: Materials in Electronics》2011,22(12):1778-1782
Bismuth-layered compound Ca0.15Sr1.85Bi4−xNdxTi5O18 (CSBNT, x = 0–0.25) ferroelectric ceramics samples were prepared by solid-state reaction method. The effects of Nd3+ doping on their ferroelectric and dielectric properties were investigated. The remnant polarization Pr of CSBNT ceramics
increases at beginning then decreases with increasing of Nd3+ doping level, and a maximum Pr value of 9.6 μC/cm2 at x = 0.05 was detected with a coercive field Ec = 80.2 kV/cm. Nd3+ dopant not only decreases the Curie temperature linearly, but also the dielectric constant (εr) and dielectric loss tangent (tan δ). The magnitudes of εr and tan δ at the frequency of 100 kHz are estimated to be 164 and 0.0083 at room temperature, respectively. 相似文献
11.
X. H. Zheng X. M. Chen T. Wang 《Journal of Materials Science: Materials in Electronics》2005,16(9):623-627
The effects of La/Sn co-substitution at A and B sites of Ba4Nd2Ti4Ta6O30 ceramics were investigated. With La/Sn co-substitution, the temperature coefficient was significantly improved to near zero, at the same time, dielectric constant reduced and dielectric loss increased. In particular, remarkable annealing effects on dielectric properties were observed for these modified ceramics. After annealing, dielectric constant considerably increased, and temperature coefficient shifted to more negative. 相似文献
12.
Mohamed M. Gomaa Hussein Darwish Saad M. Salman 《Journal of Materials Science: Materials in Electronics》2008,19(1):5-15
The ac electrical properties of some lithium silicate glasses and glass-ceramics containing varying proportions of Y2O3 and/or Fe2O3 were measured to investigate their electronic hopping mechanism. There is a clear variation of these properties with composition.
The obtained results were related to the concentration and role of Y2O3 and/or Fe2O3 in the lithium silicate glass structure. In crystalline solids the electrical properties data obtained were correlated to
the type and content of the mineral phases formed as indicated by X-ray diffraction analysis (XRD).
The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response
in the interval 30 Hz–100 KHz and the effect of compositional changes on the measured properties was investigated. The measurements
revealed that the electrical responses of the samples were different and complex. The addition of Y2O3 generally, decreased the ac conductivity, dielectric constant and dielectric losses of the lithium silicate glasses. The
addition of Fe2O3 in Y2O3-containing glasses increases the conductivity, while, the dielectric constant and dielectric losses were found to be decreased.
However, the addition of Fe2O3 instead of Y2O3 led to decrease the ac conductivity and increased their dielectric constant and dielectric losses.
The obtained data were argued to the internal structure of the lithium silicate glass and the nature or role-played by weakness
or rigidity of the structure of the sample.
Lithium disilicate-Li2Si2O5, lithium metasilicate-Li2SiO3, two forms of yttrium silicate Y2Si2O7 & Y2SiO5, iron yttrium oxide-YFeO3, lithium iron silicate-LiFeSi2O6 and α-quartz phases were mostly developed in the crystallized glasses.
The conductivity of the crystalline materials was found to be relatively lower than those of the glass. At low frequency,
as the Y2O3 content increased the ac conductivity, dielectric constant and dielectric loss data of the glass-ceramics decreased. However,
the addition of Fe2O3 to the Y2O3 containing glass-ceramic led to increase the conductivity. The addition of high content of Fe2O3 instead of Y2O3 in the glass ceramic led to increase the ac conductivity. 相似文献
13.
The electrical conductivity, dielectric permittivity, and loss tangent of a K3Li1.88Nb5.12O15.24 crystal have been measured at temperatures from 90 to 300 K and frequencies of 0.1, 1, 10, and 103 kHz. The results demonstrate that the dielectric permittivity of the crystal increases with increasing temperature and drops with increasing frequency. The plots of tanδ versus temperature show maxima characteristic of semiconductors. The conductivity of the crystal increases by several orders of magnitude with increasing frequency. The conductivity and dielectric properties of the K3Li1.88Nb5.12O15.24 crystal are shown to be anisotropic. 相似文献
14.
GUO-HUA CHEN JIN LIU XU-QIONG LI HUA-RUI XU MIN-HONG JIANG CHANG-RONG ZHOU 《Bulletin of Materials Science》2011,34(6):1233-1236
Phase purity, microstructure, sinterability and microwave dielectric properties of BaCu(B2O5)-added Li2ZnTi3O8 ceramics and their cofireability with Ag electrode were investigated. A small amount of BaCu (B2O5) can effectively reduce the sintering temperature from 1075°C to 925°C, and it does not induce much degradation of the microwave
dielectric properties. Microwave dielectric properties of ε
r = 23·1, Q × f = 22,732 GHz and τ
f = − 17·6 ppm/°C were obtained for Li2ZnTi3O8 ceramic with 1·5 wt% BaCu(B2O5) sintered at 925°C for 4 h. The Li2ZnTi3O8 +BCB ceramics can be compatible with Ag electrode, which makes it a promising microwave dielectric material for low-temperature
co-fired ceramic technology application. 相似文献
15.
W. Z. Yang C. L. Song X. Q. Liu H. Y. Zhu X. M. Chen 《Journal of Materials Science》2011,46(19):6339-6343
Single tetragonal La1.5Sr0.5CoO4 ceramics with the space group of I 4/mmm (139) were prepared by a solid-state reaction process, and dielectric characteristics were investigated on a broad frequency
and temperature range. There was one obvious dielectric relaxation around room temperature plus a low temperature upturn on
the curve of temperature dependence of dielectric properties for La1.5Sr0.5CoO4 ceramics. This dielectric relaxation was a thermal-activated process. It should be attributed to the mixed-valence structure
(Co2+/Co3+) since its activation energy was similar to that of small polaronic hopping process. After annealing the sample in O2 atmosphere, dielectric constants and ac conductivities of La1.5Sr0.5CoO4 ceramics increased and decreased after annealing the sample in N2 atmosphere. This abnormal phenomenon should be attributed to the variation of concentration for holes (Co3+). 相似文献
16.
Ashok Kumar R. S. Katiyar Ramesh Nath Premnath Carlos Rinaldi J. F. Scott 《Journal of Materials Science》2009,44(19):5113-5119
Layered nanostructures (LNs) of the commercial ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) and the natural ferroic relaxor Pb(Fe0.66W0.33)O3 (PFW) were fabricated with a periodicity of PZT/PFW/PZT (~5/1/5 nm, thickness ~250 nm) on MgO substrates by pulsed laser
deposition. The dielectric behavior of these LNs were investigated over a wide range of temperatures and frequencies, observing
Debye-type relaxation with marked deviation at elevated temperatures (>400 K). High dielectric constant and very low dielectric
loss were observed below 100 kHz and 400 K, whereas the dielectric constant decreases and loss increases with increase in
frequency, similar to relaxor ferroelectrics. Asymmetric ferroelectric hysteresis loops across UP and DOWN electric field
were observed with high remanent polarization (Pr) of about 33 μC/cm2. High imprint (~5–7 V across 250 nm thin films) were seen in ferroelectric hysteresis that may be due to charge accumulation
at the interface of layers or significant amount of strain (~3.21) across the layers. Room temperature ferromagnetic hysteresis
was observed with remanent magnetization 5.32 emu/cc and a coercive field of ~550 Oe. Temperature and field dependent leakage
current densities showed very low leakage ~10−7–10−5 A/cm2 over 500 kV/cm. We observed imprint in hysteresis that may be due to charge accumulation at the interface of layers or active
role of polar nano regions (PNRs) situated in the PFW regions. 相似文献
17.
The procedure and results of measurements of the dielectric loss tangent using the dielectric resonator technique on azimuthal
modes of the HE (quasi-E) and EH (quasi-H) types are considered. The measurements were performed for uniaxial anisotropic single crystals of Al2O3 (at a frequency of 11 GHz) and SiO2 (at 39 GHz) in a temperature range of 80–373 K and for an isotropic single crystal of Y3Al5O2 (YAG) at room temperature in a frequency range of 9–15 GHz. The proposed method revealed the anisotropy of dielectric losses
in Al2O3 and SiO2 single crystals in the temperature range studied. According to this, losses along the optical axis of these crystals are
lower than in the transverse plane. In the YAG crystal, the Q values for modes of the two types with the same frequency are close, which corresponds to isotropic losses. The dielectric
losses in YAG increase in proportion to the frequency. 相似文献
18.
Moti Ram 《Journal of Materials Science: Materials in Electronics》2012,23(4):936-939
The LiCo3/5Fe1/5Mn1/5VO4 compound was successfully synthesized by solution-based chemical method. The variation of dielectric constant (εr) with frequency at different temperatures shows a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates dielectric anomalies in εr at temperature (Tmax) = 220, 235, 245, 260 and 275 °C with (εr)max ~ 6,830, 2,312, 1,224, 649 and 305 for 10, 50, 100, 200 and 500 kHz, respectively. The variation of tangent loss with frequency
at different temperatures shows the presence of dielectric relaxation in the material. The variation of relaxation time as
a function of temperature follows the Vogel-Fulcher relation. 相似文献
19.
Wen Feng Qin Wan Yong Ai Jun Zhu Jie Xiong Jinlong Tang Ying Zhang Yan Rong Li 《Journal of Materials Science》2007,42(20):8707-8713
Conductive SrRuO3 (SRO) thin films have been grown on (100) MgO substrates by pulsed laser deposition (PLD) technique. Effects of oxygen pressure
and deposition temperature on the orientation of SRO thin film were investigated. X-ray diffraction (XRD) θ/2θ patterns and
the temperature dependent resistivity measurements indicated that oxygen pressure of 30 Pa and deposition temperature of 700 °C
were the optimized deposition parameters. A parallel-plate capacitor structure was prepared with the SRO films deposited under
optimized condition as an electrode layer and Ba0.60Sr0.40TiO3 (BST) thin film as the dielectric layer. XRD Φ scans indicated a
epitaxial relationship between BST and SRO on MgO substrate. The dielectric constant and loss tangent measured at 10 kHz
and 300 K was 427 and 0.099 under 0 V bias, and 215 and 0.062 under 8 V bias, respectively. A tunability of 49.6% has been
achieved with DC bias as low as 8 V. The C–V hysteresis curve and the P–E hysteresis loop suggested that the BST films epitaxially grown on SRO/MgO have ferroelectricity at room temperature. The
induced ferroelectricity was believed to originate from the compressive strain between the epitaxial BST and SRO thin films.
These results show the potential application of the BST/SRO heterostructures in microelectronic devices. 相似文献
20.
Ba0.6Sr0.4TiO3 dielectric thin films doped by Cr(0, 1, 2.5, 5, 10 mol%) (BSTC) were prepared by radio frequency magnetron sputtering on
Pt/Ti/SiO2/Si substrates. The structure and morphology of the BSTC thin films were studied by atomic force microscopy and X-ray diffraction.
The effect of Cr doping on the dielectric properties of BST thin films were analyzed. The results show that the dielectric
loss of Cr doping BST thin films is lower than that undoped, and the tunability increased with Cr doping. The thin film doped
with 5 mol% Cr has the best dielectric properties. The tunability, loss and figure of merit (FOM) at 1 MHz were 38.9%, 0.0183,
and 21.3, respectively. 相似文献