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1.
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
2.
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
3.
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
4.
Pure and Zr-substituted CaCu3(Ti1−x
Zr
x
)4O12 (x = 0, 0.01, 0.02, 0.03) ceramics were prepared by the Pechini method. X-ray powder diffraction analysis indicated the formation
of single-phase compound, and all the diffraction peaks were completely indexed by the body-centered cubic perovskite-related
structure. The effects of Zr4+ ion substituting partially Ti4+ ion on the dielectric properties were investigated in frequency range between 100 Hz and 1 GHz. The low frequency (f ≤ 105 Hz) dielectric constant decreases with Zr substitution and the high frequency (f ≥ 107 Hz) dielectric constant is unchanged. Interestingly, a low-frequency relaxation was observed at room temperature through
Zr substitution. The observed dielectric properties in Zr-substituted samples were discussed using the internal barrier layer
capacitor model. A corresponding equivalent circuit was adopted to explain the dielectric dispersion. The characteristic frequency
of low-frequency relaxation rises due to the decrease of the resistivity of grain boundary with Zr substitution, which is
likely responsible for the large low-frequency response at room temperature. 相似文献
5.
Haibo Yang Ying Lin Jianfeng Zhu Fen Wang 《Journal of Materials Science: Materials in Electronics》2010,21(4):368-372
Dense Ca(Zn1/3Nb2/3)O3/NiZn ferrite composites with homogeneously fine microstructures were prepared through conventional solid-state method. The
powder XRD patterns confirm the coexistence of the two phases. The dielectric properties in the low frequency range (100 Hz–1 MHz)
follow the rule of Maxwell–Wagner interfacial polarization. The dielectric and magnetic properties in the high frequency range
(10 MHz–1 GHz) are also reported. The results show that this kind of magnetic–dielectric composites could be used in high-frequency
communications for the capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. 相似文献
6.
Oxides of the type, Ba3-xSrxZnNb2O9 (0 ≤x ≤3), were synthesized by the solid state route. Oxides calcined at 1000°C show single cubic phase for all the compositions.
The cubic lattice parameter (a) decreases with increase in Sr concentration from 4.0938(2) forx = 0 to 4.0067(2) forx = 3. Scanning electron micrographs show maximum grain size for thex = 1 composition (∼ 2 μm) at 1200°C. Disks sintered at 1200°C show dielectric constant variation between 28 and 40 (at 500
kHz) for different values of x with the maximum dielectric constant atx = 1. 相似文献
7.
Monophasic CaNaBi2Nb3O12 powders were synthesized via the conventional solid-state reaction route. Rietveld refinement of the X-ray powder diffraction
(XRD) data and selected area electron diffraction (SAED) studies confirmed the phase to be a three-layer Aurivillius oxide
associated with an orthorhombic B2cb space group. The dielectric properties of the ceramics have been studied in the 300–800 K temperature range at various frequencies
(1 kHz to 1 MHz). A dielectric anomaly was observed at 676 K for all the frequencies corresponding to the ferroelectric to
paraelectric phase transition as it was also corroborated by the high temperature X-ray diffraction studies. The incidence
of the polarization–electric field (P vs. E) hysteresis loop demonstrated CaNaBi2Nb3O12 to be ferroelectric. 相似文献
8.
Feifei Wang Min Xu Tao Wang Yanxue Tang Wangzhou Shi 《Journal of Materials Science》2012,47(5):2352-2358
Phase transition and electrical properties were demonstrated for a Li-modified Bi0.5Na0.5TiO3-based solid solution. (0.935 − x)Bi0.5Na0.5TiO3 − xBi0.5Li0.5TiO3 − 0.065BaTiO3 with 0.5 mol% Mn doping was prepared by a conventional solid state reaction method. Close inspection of X-ray diffraction
patterns indicated that no characteristic peaks splitting happened, indicating the pseudocubic structure for all the compositions.
At a critical composition x of 0.06, optimized performance was obtained with piezoelectric constant d
33 of 176 pC/N, electromechanical coupling factors k
P of 0.33, and k
t of 0.52, respectively. In addition, it was found that the Li substitution could lead to a disruption of long-range ferroelectric
order and obtain enhanced frequency dispersion behavior accompanied with the decreasing of the depolarization temperature
T
d, which was responsible for the observed weaker ferroelectric polarization and electromechanical response. The composition
induced structure evolution was also discussed combined with the Raman spectroscopy. 相似文献
9.
Yean Wang Yunbo Wang Wei Rao Meng Wang Gangxian Li Yubin Li Junxiong Gao Wenli Zhou Jun Yu 《Journal of Materials Science: Materials in Electronics》2012,23(5):1064-1071
The (1 − x)Ba0.8Sr0.2TiO3–xCoFe2O4 ceramic composites (x = 0–1) were prepared by standard solid state reaction method. X-ray diffraction and SEM indicate the Ba0.8Sr0.2TiO3 (BST) phase and CoFe2O4 (CFO) phase coexist in the composites. The dielectric constant and dielectric loss for the composites were studied as a function
of frequency (40 Hz–1 MHz) and temperature (30–600 °C). Magnetic and ferroelectric tests show that the ceramic composites
display ferromagnetic and ferroelectric properties simultaneously. The saturated polarization of the composites decrease with
ferrite concentration increasing, while the remnant polarization of the composites increase with increasing ferrite concentration.
The enhanced ferroelectricity of composites may be attributed to space charge contribution in the composites. 相似文献
10.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan 《Journal of Materials Science: Materials in Electronics》2010,21(4):364-367
Perovskite lead-free piezoelectric ceramics Bi0.5Na0.5TiO3, modified with yttrium and manganese to form a new compound, (1 − x) Bi0.5Na0.5TiO3–xYMnO3 (BNT-YM100x) with x = 0–1.2 mol%, was synthesized by a conventional solid-state reaction method. The effect of YMnO3 on crystal structure, dielectric and piezoelectric properties was investigated. X-ray diffraction analysis shows that the
materials have a single phase perovskite structure with rhombohedral symmetry. Addition of small amount of YMnO3 improves piezoelectric properties and the optimal piezoelectric properties of d
33 = 115 pC/N, k
p = 0.207 and Q
m = 260 were obtained at 0.9% YMnO3 addition. The loss tangent tanδ is approximately constant while Curie temperature decreases with increasing YMnO3 concentration. 相似文献
11.
A.c. measurements were preformed on bulk samples of Ca1−x
Sr
x
TiO3 (CST) perovskites with x = 0, 0.1 and 0.5 as a function of temperature range 300–450 K and frequency range 103–105 Hz . The experimental results indicate that the a.c. conductivity σa.c.(ω), dielectric constant ε′ and dielectric loss ε′′ depend on the temperature and frequency. The a.c. conductivity as a function
of frequency is well described by a power law Aω
S
with s the frequency exponent. The obtained values of s > 1 decrease with increasing temperature. The present results are compared to the principal theories that describe the universal
dielectric response (UDR) behavior. 相似文献
12.
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
13.
Effects of Fe and La addition on the dielectric, ferroelectric, and piezoelectric properties of Bi0.5Na0.5TiO3–Bi0.5Li0.5TiO3–BaTiO3–Mn ceramics were investigated. Similar to the doping effect in lead-based piezoelectric materials, here the Fe-doped ceramic
created a hard effect with an improved mechanical quality factor (Q
m) ~ 160, coercive field (E
c) ~ 2.9 kV/mm, decreased dielectric constant ( e33T /e0 ) ~ 80 3, \left( {\varepsilon_{33}^{T} /\varepsilon_{0} } \right)\sim 80 3, and loss (tanδ) ~ 0.024 while the La-doped one indicated a soft feature with improved piezoelectric constant (d
33) ~ 184 pC/N, e33T /e0 ~ 983, \varepsilon_{33}^{T} /\varepsilon_{0} \,\sim { 983}, tanδ ~ 0.033, and decreased E
c ~ 2.46 kV/mm. In addition, the temperature dependence of the ferroelectric hysteresis loops and strain response under unipolar
electric field was also studied. Around the depolarization temperature T
d, large strain value was obtained with the normalized d33* d_{33}^{*} up to ~1,000 pC/N, which was suggested originated from the development of the short-range order or non-polar phases in the
ferroelectric matrix. All these would provide a new way to realize high piezoelectric response for practical application in
different temperature scale. 相似文献
14.
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
15.
Guo-hua Chen Jie-chang Di Ming Li Ian M. Reaney Yan Lei Hua-rui Xu Chang-rong Zhou Min-hong Jiang Xin-yu Liu 《Journal of Materials Science: Materials in Electronics》2012,23(3):746-752
Ca4-xMgxLa2Ti5O17
ceramics were prepared by a solid state ceramic route for x = 0, 0.5, 1, 2, 3 and 4. The structure and microstructure of the ceramics were investigated using X-ray diffraction, scanning
electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction results show that the Ca4-x
Mg
x
La2Ti5O17 adopts an orthorhombic crystal structure with no secondary phase observed for x from 0 to 0.5. Secondary phase, MgTiO3 occurs with further increasing doping level (1 ≤ x ≤ 3). When x = 4, mixture phases La0.66TiO2.993, MgTiO3 and a trace of unknown phase coexist. Ca4La2Ti5O17 ceramic exhibits a relative permittivity (εr) ~ 65, quality factor (Q × f) ~13,338 GHz (at ~4.75 GHz), and temperature coefficient of resonant frequency (τ
f
) ~ 165 ppm/°C. The sintering temperature was distinctly reduced from 1,580 °C for x = 0 to 1,350 °C for x = 4. With increasing Mg content, εr and τf obviously decrease, while Q × f value initially decreases and then increases. The ceramic for x = 2 shows εr ~ 50, Q × f ~ 9,451 and τ
f
~ 62.5 ppm/°C. By the complete replacement of Ca with Mg, Mg4La2Ti5O17 ceramic sintered at 1,350 °C for 4 h combines a high dielectric permittivity (ε
r
= 31), high quality factor (Q × f ~ 15,021) and near-zero temperature coefficient of resonant frequency (τ
f
~ 4.0 ppm/°C). The materials are suitable for microwave applications. 相似文献
16.
M. M. El-Nahass E. A. A. El-Shazly A. M. A. El-Barry H. S. S. Omar 《Journal of Materials Science》2011,46(17):5743-5750
Cadmium thiogallate CdGa2S4 thin films were prepared using a conventional thermal evaporation technique. The dark electrical resistivity calculations
were carried out at different elevated temperatures in the range 303–423 K and in thickness range 235–457 nm. The ac conductivity
and dielectric properties of CdGa2S4 film with thickness 457 nm has been studied as a function of temperature in the range from 303 to 383 K and in frequency
range from 174 Hz to 1.4 MHz. The experimental results indicate that σac(ω) is proportional to ω
s
and s ranges from 0.674 to 0.804. It was found that s increases by increasing temperature. The results obtained are discussed in terms of the non overlapping small polaron tunneling
model. The dielectric constant (ε′) and dielectric loss (ε″) were found to be decreased by increasing frequency and increased
by increasing temperature. The maximum barrier height (W
m) was estimated from the analysis of the dielectric loss (ε″) according to Giuntini’s equation. Its value for the as-deposited
films was found to be 0.294 eV. 相似文献
17.
Investigation of solid solution of barium-strontium orthotitanates of the type, Ba2-x
Sr
x
TiO4 (0 ≤x≤ 2), show that pure phases exist only for the end members, Ba2TiO4 and Sr2TiO4, crystallizing in the β-K2SO4 and K2NiF4 structures, respectively. The intermediate compositions (till≥ 1) lead to a biphasic mixture of two Ba2TiO4-type phases (probably through a spinodal decomposition) with decreasing lattice parameters, indicating Sr-substitution in
both the phases. Forx > 1, Sr2TiO4 along with a secondary phase is obtained. The dielectric constant and dielectric loss were found to decrease with Sr substitution
till the nominal composition ofx = 1. However, pure Sr2TiO4 shows higher dielectric constant compared to the solid solution composition. Sr2TiO4 shows very high temperature stability of the dielectric constant. 相似文献
18.
Temperature and frequency dependence dielectric permittivity of Ba0·95Dy0·05TiO3 ceramic has been studied in the temperature range of 100–350 K at the frequencies, 1 kHz, 10 kHz, 100 kHz and 1 mHz. Diffuse
phase transition and frequency dispersion is observed in the permittivity-vs-temperature plots. This has been attributed to
the occurrence of relaxor ferroelectric behaviour. The observed relaxor behaviour has been quantitatively characterized based
on phenomenological parameters. A comparison with the Zr doped BaTiO3 has also been presented. The microstructure of as-sintered samples shows a dense and almost uniform micrograph without any
impurity phases; the grains are almost spherical with random orientation. 相似文献
19.
Pellets of ceramic Na1−xKxNbO3 (x = 0, 0.2 and 0.5), were prepared by conventional solid-state reaction method. Prepared samples were characterized using
XRD and SEM. The frequency and temperature variation of dielectric constant, loss tangent and dielectric conductivity of prepared
samples were measured in the frequency range from 10 KHz-1 MHz, and in the temperature range from 50–250°C for x = 0.2 and
0.5, and between 50 and 480°C for x = 0 compositions. It was observed that the dielectric constant and loss tangent decrease,
and conductivity increases with increasing frequency. Near the transition temperature the material shows anomalous behaviour
for the observed properties, and the peaks of dielectric constant and loss tangent were observed shifting towards lower temperature
with increasing frequency. 相似文献
20.
Ba(Ti(0.9)Sn0.1)O3 (BTS) ceramic was prepared by a conventional ceramic processing. BTS-polycarbonate (PC) composites were prepared at different
BTS concentrations by weight in order to study their optical and dielectric properties. The absorption coefficient (α) was determined in the wavelength range from 250–600 nm at room temperature for all BTS-PC composites. The optical gap (E
opt) was also determined for BTS-PC composites. The variation of the absorption coefficient (α) and optical gap (E
opt) with BTS content are reported. It was found that BTS ceramic highly enhances the UV absorption of PC host at 300 nm. The
optical gap decreases up to the value of 3.93 eV as BTS content increases up to 35 wt% and this was attributed to the formation
of localized states in the forbidden gap. The relative dielectric permittivity, dielectric loss and loss tangent were measured
at temperature range from room temperature up to 150°C and at frequency values 1 kHz, 10 kHz and 50 kHz. Addition of BTS to
PC host, however, will increase relative dielectric permittivity, dielectric loss and loss tangent. Besides, increasing of
temperature will also increase relative dielectric permittivity, dielectric loss and loss tangent especially above the glass
transition temperature of PC host and this behaviour was attributed to the segmental motion of polymer chains. On the other
hand, this study shows that there is a good agreement between SEM, DSC and dielectric results and also between optical gap
and a.c. conductivity results. Moreover, SEM and DSC results reveal that addition of BTS ceramic particles to PC host will
reduce the physical bond between polymer chains or may be will increase the free volume in the polymer host and consequently
will enhance the segmental motion of polymer chains and this behaviour is independent of ceramic phase. 相似文献