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1.
S.K. Barik P.K. Mahapatra R.N.P. Choudhary 《Applied Physics A: Materials Science & Processing》2006,85(2):199-203
Na1/2La1/2TiO3 (NLT) ceramic was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis (XRD) suggested the formation of a single-phase orthorhombic structure. SEM micrograph of the material showed uniform grain distribution on the surface of the sample. The dielectric permittivity and the loss tangent of the sample were measured in a frequency range from 1 kHz to 1 MHz and a temperature range 28 °C to 525 °C. Electrical properties of the material were studied using an ac impedance spectroscopic technique. Detailed analysis of the impedance spectrum suggested that the electrical properties of the material are strongly temperature dependant. The Nyquist plots clearly showed the presence of both bulk and grain boundary effect in the compound. The activation energy was estimated to be 1.1 eV from the temperature variation of dc conductivity. The a.c. conductivity spectrum suggests a typical signature of ion conducting system. PACS 77.22.Ch; 77.22.Gm; 77.80.Bh; 77.22.Ej 相似文献
2.
《Current Applied Physics》2009,9(2):380-383
The polycrystalline sample of Na1/2Dy1/2TiO3 ceramic was prepared by a standard high-temperature solid-state reaction technique. X-ray structural analysis confirmed the formation of single-phase (with minor secondary phase) compound in the orthorhombic (distorted tetragonal) crystal system at room temperature. Study of surface morphology by scanning electron microscope exhibits uniform distribution of rectangular/cubical grains with less voids. The elemental composition of the prepared compound was confirmed by energy dispersive X-ray spectroscopy microanalysis. Detailed studies of dielectric properties exhibit a dielectric anomaly at 94 °C suggesting a possible ferroelectric–paraelectric phase transition in the compound. The activation energy (Ea), calculated from the temperature dependence of ac conductivity plot, was found to be small (∼0.1 eV) in low temperature and large (∼0.5 eV) in high temperature region. 相似文献
3.
S.H. Choy X.X. Wang H.L.W. Chan C.L. Choy 《Applied Physics A: Materials Science & Processing》2007,89(3):775-781
Lead-free (0.90-x)(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-x(Bi1/2Li1/2)TiO3-0.05BaTiO3 piezoelectric ceramics (abbreviated as BNKLBT-100x, with x ranged from 0 to 2.5 mol %) were prepared by a conventional mixed
oxide method. Effects of the amount of (Bi1/2Li1/2)TiO3 (BLT) on the electrical properties and crystal structure of the BNKLBT ceramics were examined. BNKLBT-1.5 ceramics have good
properties with piezoelectric constant d33=163 pC/N, electromechanical coupling factor kp=0.33, kt=0.53, relative permittivity εr=785 and dissipation factor cosδ=2.2% at 1 kHz. The sample has larger remnant polarization than BNKLBT-0 ceramics and the
same coercive field as BNKLBT-0 ceramics. X-ray diffraction analysis shows that the incorporated BLT diffuses into the BNT–BKT–BT
lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry
at higher BLT amounts. Depolarization temperature (Td) of the BNKLBT-100x ceramics increases from 102 °C to ∼136 °C for BNKLBT-0 to BNKLBT-2.5. BNKLBT-1.5 is used as the transduction
element in compressive type accelerometer and its sensitivity is calibrated by the back-to back method. Within the ±2.5% tolerance,
the lead-free accelerometer has a mean value of 2.97 pC/ms-2 within 50 Hz–12.45 kHz and the lead-based accelerometer has a mean value of 4.34 pC/ms-2 within 50 Hz to 8.24 kHz.
PACS 77.22.Ej; 77.84.-s; 85.50.-n 相似文献
4.
《Current Applied Physics》2020,20(7):835-840
Acoustic anomalies of relaxor ferroelectric Na1/2Bi1/2TiO3 single crystals were investigated over a wide temperature range from −196 °C to 900 °C by using Brillouin spectroscopy. The longitudinal sound velocity, the acoustic absorption coefficient and the elastic constant C11 were determined for the acoustic phonon mode propagating in the [100] direction. Two acoustic anomalies, weaker ones at the cubic-tetragonal phase transition temperature of ~540 °C and more pronounced ones at temperatures near 315 °C near the dielectric maximum temperature, were investigated and discussed in relation with the relevant order parameters coupled to the acoustic waves. The relaxation dynamics in the cubic phase were studied based on the flattening of the mode frequency and the half width, which was observed for the first time, and a modified Arrhenius law. 相似文献
5.
S.K. Barik R.N.P. Choudhary P.K. Mahapatra 《Applied Physics A: Materials Science & Processing》2007,88(1):217-222
Complex impedance analysis of a valence-compensated perovskite ceramic oxide Na1/2Sm1/2TiO3, prepared by a mixed oxide (solid-state reaction) method, has been carried out. The formation of single-phase material was
confirmed by X-ray diffraction studies, and it was found to be an orthorhombic phase at room temperature. In a scanning electron
microscope, grains separated by well-defined boundaries are visible, which is in good agreement with that of impedance analysis.
Alternating current impedance measurements were made over a wide temperature range (31–400 °C) in an air atmosphere. Complex
impedance and modulus plots helped to separate out the contributions of grain and grain boundaries to the overall polarization
or electrical behavior. The physical structure of the samples was visualized most prominently at higher temperatures (275 °C)
from the Nyquist plots showing inter- and intragranular impedance present in the material. The frequency dependence of electrical
data is also analyzed in the framework of the conductivity and modulus formalisms. The bulk resistance, evaluated from the
impedance spectrum, was observed to decrease with rise in temperature, showing a typical negative temperature coefficient
of resistance-type behavior like that of semiconductors. The modulus mechanism indicates the non-Debye type of conductivity
relaxation in the materials, which is supported by the impedance data.
PACS 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.22.Jp; 77.84.Bw 相似文献
6.
S.U. Adikary A.L. Ding H.L.W. Chan 《Applied Physics A: Materials Science & Processing》2002,75(5):597-600
BaxSr1-xTiO3 thin films with a compositional gradient of x=0.3 to 1 (in 0.1 mole fraction increments) were fabricated on Pt/Ti/SiO2/Si substrates using a modified sol–gel technique. The graded film crystallised in a perovskite structure and consists of
a uniform microstructure with comparatively larger grains. The room-temperature relative dielectric constant (εr) and dielectric loss (cosδ) at 100 kHz were found to be 305 and 0.03 respectively. Dielectric peaks were not observed in
the temperature range from -20 °C to 120 °C. The dielectric constant and dielectric loss were almost independent of temperature.
Polarisation–electric field measurements at room temperature revealed a saturated but slim hysteresis loop with a remanent
polarisation (Pr) of 0.6 μC/cm2 and a coercive field (Ec) of 2.4 kV/mm. The graded film behaves as a stack of BaxSr1-xTiO3 capacitors connected in series and hence the dielectric Curie peaks are removed.
Received: 4 October 2001 / Accepted: 17 October 2001 / Published online: 23 January 2002 相似文献
7.
Yang Qiu Songliu Yuan Zhaoming Tian Liang Chen Chuanhui Wang Hanning Duan Kai Guo 《Applied Physics A: Materials Science & Processing》2012,107(2):379-383
Single phase Bi1/2Na1/2Cu3Ti4O12 (BNCTO) ceramics with different grain sizes (1.4–4.3 μm) are prepared by a modified Pechini method to investigate their giant
dielectric and nonlinear electrical behaviors. The results show that the giant dielectric and nonlinear electrical behaviors
are strongly dependent on grain size. With the increment of grain size, the dielectric constant increases monotonically from
14110 (for 1.4 μm sample) to 36183 (for 4.3 μm sample) at 1 kHz, in accompaniment with the breakdown voltage reducing from
112.5 to 43.2 V/mm and the nonlinear coefficient reducing from 4.9 to 3.4. On the basis of the internal barrier layer capacitor
(IBLC) model and the IBLC model of Schottky-type potential barrier, an interpretation of the grain size effect on the giant
dielectric and nonlinear electrical behaviors is presented. 相似文献
8.
Laijun Liu Yanmin Huang Congxue Su Liang Fang Meixia Wu Changzheng Hu Huiqing Fan 《Applied Physics A: Materials Science & Processing》2011,104(4):1047-1051
Sodium potassium niobate K0.5Na0.5NbO3(KNN) ceramic was synthesized by a solid-state technique. The X-ray diffraction of the sample at room temperature showed a
monoclinic phase. The real part (ε′) and imaginary part (ε″) of dielectric permittivity of the sample were measured in a frequency range from 40 Hz to 1 MHz and in a temperature range
from 350 to 850 K. The ε′ deviated from Curie–Weiss law above 702 K, due to additional dielectric contributions resulting from universal dielectric
response and thermally activated space charges at high temperatures. This anomaly arose from a Debye dielectric dispersion
that slowed down following an Arrhenius law. We have established a link between the dielectric relaxation and the conductivity. 相似文献
9.
S.H. Choy X.X. Wang C.P. Chong H.L.W. Chan P.C.K. Liu C.L. Choy 《Applied Physics A: Materials Science & Processing》2006,84(3):313-316
Lead-free piezoelectric ceramic 0.90(Bi1/2Na1/2)TiO3–0.05(Bi1/2K1/2)TiO3–0.05BaTiO3 (BNKBT-5) rings (OD=12.7 mm, ID=5.1 mm and 2.3-mm thick) were fabricated and characterized. Four ceramic rings were used as the driving element in an ultrasonic wirebonding transducer and the performance of the transducer was characterized. The lead-free transducer was found to have comparable voltage rise and fall times as a lead-based PZT transducer and has a relatively large vibration amplitude, thus showing that BNKBT-5 has the potential to be used in fabricating lead-free ultrasonic wirebonding transducers. PACS 77.22.Ej; 77.84.-s; 85.50.-n 相似文献
10.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
11.
A precursor of TiO2–LiCo1/3Ni1/3Mn1/3O2 was prepared by electrostatic self-assembly method. The final product was obtained by heating the precursor at 400–450 °C
for 4–6 h in air. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and
electrochemical tests were used to examine the structural, morphology, elementary valence, and electrochemical characteristics.
XRD indicated that the TiO2-coated material can be indexed by α-NaFeO2 layered structure, which belongs to hexagonal-type space group R3m. XPS results confirmed the existence of TiO2 compound on the surface of the coated sample. The SEM image showed that the material had spherically porous morphology with
the uniform size about 6 μm. The initial charge–discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 material was 168.8/160.0 mAh/g. After 60 cycles, the discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 sample was 147.0 mAh/g, and the coulombic efficiency was 94.0%. Compared with the uncoated sample, the electrochemical performance
of TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was improved. 相似文献
12.
45% semi-crystalline parylene-C (–H2C–C6H3Cl–CH2–)
n
thin films (5.8 μm) polymers have been investigated by broadband dielectric spectroscopy for temperatures above the glass
transition (T
g
=90°C). Good insulating properties of parylene-C were obtained until operating temperatures as high as 200°C. Thus, low-frequency
conductivities from 10−15 to 10−12 S/cm were obtained for temperatures varying from 90 to 185°C, respectively. This conductivity is at the origin of a significant
increase in the dielectric constant at low frequency and at high temperature. As a consequence, Maxwell–Wagner–Sillars (MWS)
polarization at the amorphous/crystalline interfaces is put in evidence with activation energy of 1.5 eV. Coupled TGA (Thermogravimetric
analysis) and DTA (differential thermal analysis) revealed that the material is stable up to 400°C. This is particularly interesting
to integrate this material for new applications as organic field effect transistors (OFETs). Electric conductivity measured
at temperatures up to 200°C obeys to the well-known Jonscher law. The plateau observed in the low frequency part of this conductivity
is temperature-dependent and follows Arrhenius behavior with activation energy of 0.97 eV (deep traps). 相似文献
13.
F. Capel C. Moure P. Durán A.R. González-Elipe A. Caballero 《Applied Physics A: Materials Science & Processing》1999,68(1):41-48
2 -doped YTZP ([%mol]3 Y2O3) compositions sintered in the temperature range of 1300 to 1450 °C, the tetragonal zirconia solid solutions field for the
ZrO2-Y2O3-TiO2 system was established. The solubility of TiO2 in YTZP was found to be about 12–[%mol]14 at 1450 °C. Structural characterization of the Ti-YTZP tetragonal zirconia solid
solutions was carried out using X-ray absorption spectroscopy (EXAFS and XANES) to provide information on the environment
of Ti atoms. The electrical behavior in air of the TiO2-doped tetragonal zirconia solid solutions was studied by impedance spectroscopy in the temperature range of 300 to 800 °C,
and it was found that the ionic conductivity decreases with increasing titania content. EXAFS and XANES results show that
as the Ti4+ ions dissolve into the tetragonal zirconia YTZP matrix, a displacement of Ti ions from the center of symmetry takes place,
leading to a non-random substitution of Ti4+ ions on Zr4+ lattice sites. Ti-O bond distances derived from EXAFS indicate that the Ti ion can be in a square-pyramidal arrangement,
i.e., fivefold oxygen-coordinated. As a consequence two kinds of cation–oxygen vacancy associations are created; the high-mobility
oxygen-vacancy–eightfold-coordinated cation (Zr4+) and the low-mobility oxygen-vacancy–fivefold-coordinated cation (Ti4+). This results in a decrease in the global concentration of moving oxygen vacancies and, therefore, in a decrease of the
electrical conductivity.
Received: 1 April 1998/Accepted: 28 September 1998 相似文献
14.
Polycrystalline BaCo1/2W1/2O3 (BCW) is prepared by the solid-state reaction technique. The X-ray diffraction study of the compound at room temperature reveals the monoclinic phase. The field dependence of the dielectric constant and the conductivity are measured in the frequency range from 50 Hz to1 MHz and in the temperature range from 300 to 413 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency is performed. The frequency-dependent maxima in the imaginary impedance are found to obey an Arrhenius law with an activation energy=0.86 eV. The frequency-dependent electrical data are also analysed in the framework of the conductivity and modulus formalisms. 相似文献
15.
N. M. Olekhnovich A. V. Pushkarev Yu. V. Radyush 《Journal of Applied Spectroscopy》2009,76(4):518-522
A technique for analysis of the electric modulus spectrum of dielectric ceramics based on the elimination of the direct current
conductivity (σ
dc
) contribution has been developed. Expressions are given for the real (M′
ac
) and imaginary (M′′
ac
) parts of the complex electrical modulus related only to the dielectric polarization and not containing the contribution
of σ
dc
. The frequency dependence of M′′
ac
and the M′′
ac
– M′
ac
diagram for BiMg1/2Ti1/2O3 and BiMg1/2Zr1/2O3 perovskite ceramics are analyzed. 相似文献
16.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
17.
Huanfu Zhou Hong Wang Minghui Zhang Xi Yao 《Applied Physics A: Materials Science & Processing》2009,95(2):513-516
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 5.5:1:7 was prepared by solid state reaction route. The phase and structure of the ceramic were characterized
by X-ray diffraction and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied
using a network analyzer. The microwave dielectric ceramic has low sintering temperature (∼1075°C) and good microwave dielectric
properties of ε
r=42, Q×f=16900 GHz (5.75 GHz), and τ
f
=63.7 ppm/°C. The addition of B2O3 can effectively lower the sintering temperature from 1075 to 875°C and does not induce degradation of the microwave dielectric
properties. Obviously, the LNT ceramics can be applied to microwave low temperature-cofired ceramics (LTCC) devices. 相似文献
18.
Ce0.9Gd0.1O1.95 (GCO), is one of the potential candidate electrolytes for intermediate temperature Solid Oxide Fuel Cells (ITSOFC). GCO has
high oxide ion conductivity in the intermediate temperature range (500 – 700 °C) compared to other Ce1−yGdyO2-2/y compositions and the Gd3+ ion is the most appropriate dopant material compared to other rare earth materials such as Sm3+, Y3+, Zr3+, etc. Our results show that the fuel cell H2/Pt/Ce0.9Gd0.1O1.95/Pt/O2 operated in the temperature range 500 – 700°C gives the maximum power densities 0.0049 W/cm2 at 500 °C and 0.0126 W/cm2 at 650 °C for cell voltages 0.6275 V and 0.6278 V, respectively, where the electrolyte was kept in 5% H2 (+ Argon) for 12 hours before use in the fuel cell. Maximum power densities are 0.0038 W/cm2 at 500 °C and 0.0270 W/cm2 at 650 °C for cell voltages 0.5986 and 0.5913 V, respectively, where the electrolyte was kept in 2 % O2 (+ Argon) for 12 hours before use in the fuel cell.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
19.
X.X. Wang X.G. Tang K.W. Kwok H.L.W. Chan C.L. Choy 《Applied Physics A: Materials Science & Processing》2005,80(5):1071-1075
(Bi1/2Na1/2)TiO3 ceramics (BNT) with 0–6 mol% of excess Bi2O3 are prepared by conventional solid-state sintering. The electrical properties of the samples are examined. The addition of excess Bi2O3 reduces the leakage current of BNT ceramics significantly, thus facilitating the poling process, and improves their piezoelectric properties slightly for certain amounts of added Bi2O3. BNT ceramics have very high dielectric constants and dissipation factors at low frequency and high temperature due to their high conductivity. Adding excess Bi2O3 to BNT ceramics affects their dielectric behavior and phase transition temperatures. Grain growth is suppressed by adding Bi2O3 and no second phase is observed for BNT ceramics with up to 6 mol% of excess Bi2O3 added. 相似文献
20.
Thin film of CaCu3Ti4O12 (CCTO) has been deposited on Nb-doped SrTiO3(100) single crystal using pulsed laser deposition. The dielectric constant and AC conductivity of CCTO film in the metal–insulator–metal
capacitor configuration over a wide temperature (80 to 500 K) and frequency (100 Hz to 1 MHz) range have been measured. The
small dielectric dispersion with frequency observed in the lower temperature region (<300 K) indicates the presence of small
defects in the deposited CCTO thin film. The frequency-dependent AC conductivity at lower temperature indicates the hopping
conduction. The dielectric dispersion data has been analyzed in the light of both conductivity relaxation and Debye type relaxation
with a distribution of relaxation times. Origin of dielectric dispersion is attributed to the distribution of barrier heights
such that some charge carriers are confined between long-range potential wells associated with defects and give rise to dipolar
polarization, while those carriers which do not encounter long-range potential well give rise to DC conductivity. 相似文献