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1.
Huanfu Zhou Xiuli Chen Liang Fang Changzheng Hu Hong Wang 《Journal of Materials Science: Materials in Electronics》2010,21(9):939-942
Ba5Nb4O15 powders were synthesized by molten-salt method in NaCl–KCl flux at a low temperature of 650–900 °C for 2 h, which is lower
than that of the conventional solid-state reaction. This simple process involved mixing of the raw materials and salts in
a certain proportion. Subsequent calcination of the mixtures led to Ba5Nb4O15 powders at 650–900 °C. XRD and SEM techniques were used to characterize the phase and morphology of the fabricated Ba5Nb4O15 powders, respectively. After sintering at 1,300 °C for 2 h, the densified Ba5Nb4O15 ceramics with good microwave dielectric properties of εr = 39.2, Q × f approximated as 27,200 GHz and τ
f
= 72 ppm/°C have been obtained. 相似文献
2.
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
3.
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
4.
Junji Zhang Jumei Yu Mingju Chao Erjun Liang Mingyu Li Dechuan Li 《Journal of Materials Science》2012,47(3):1554-1558
Textured poly crystalline barium dititanate BaTi2O5 (BT2) ceramics with a preferred 〈010〉 orientation were synthesized by laser rapid solidification method, with a CO2 laser. The 〈010〉 orientation of the BT2 is along the laser incident direction, and the orientation factor (f) and relative density of the unannealed BT2 sample are 0.40 and 96.2%, respectively. The two quantities increase with increasing
annealing time, and reach the maximum values of 0.42 (annealed at 1,000 °C for 12 h) and 97.5% (annealed at 1,000 °C for 24 h),
respectively. The images of scanning electron microscopy reveal that the BT2 are composed of flake-like microstructures with
the maximum thickness of 20 μm and dimension of 0.6 mm, which are parallel to the laser incident direction. The measured Curie
temperature (T
c) and the maximum dielectric constant (εmax) are 443 and 6,000 °C, respectively. 相似文献
5.
Synthesis and dielectric properties of BiFeO<Subscript>3</Subscript> derived from molten salt method
X. H. Zheng P. J. Chen N. Ma Z. H. Ma D. P. Tang 《Journal of Materials Science: Materials in Electronics》2012,23(5):990-994
BiFeO3 powder was synthesized in NaCl media at temperature range from 700 to 800 °C, using Bi2O3 and Fe2O3 as raw materials. Effects of calcining temperature and salt ratios on the synthesis of BiFeO3 powder had been investigated. It was found that NaCl effectively promoted the formation of BiFeO3. Almost pure BiFeO3 phase with a very small amount of Bi2Fe4O9 phase was synthesized at 750 °C with salt weight ratios of 1:1. A large amount of BiFeO3 phase decomposed to Bi2Fe4O9 and Bi25FeO39 phase when the temperature was up to 800 °C. In the present method, the calcining temperature played an important role in
the formation of BiFeO3 phase. BiFeO3 ceramics derived from molten salt method were prepared and exhibited the higher dielectric constant. 相似文献
6.
Jingdong Guo Weibing Ma Minjie Ma Huaidang Zhao Yixuan Yang Jifeng Gao 《Journal of Materials Science: Materials in Electronics》2018,29(5):3640-3647
Microwave dielectric properties and microstructures of ultra-low loss Li2Mg3TiO6 ceramic prepared by reaction-sintering method (RS) and conventional solid-state reaction method (CS) have been investigated. The XRD patterns and SEM images revealed that the single phase of Li2Mg3TiO6 and uniform morphology are obtained by both RS and CS methods at the optimal sintering temperatures. In order to further investigate the effects of different sintering methods on the microwave dielectric properties of Li2Mg3TiO6 ceramics, the oxide polarizabilities and packing fraction were calculated based on the Rietveld refinement. The calculation results revealed that the RS method was more beneficial to the microwave dielectric properties of Li2Mg3TiO6 ceramics in comparison with CS method. Excellent microwave dielectric properties for Li2Mg3TiO6 ceramics with enhanced Q?×?f value of 157,036 GHz could be obtained using RS method sintered at 1250 °C for 6 h. 相似文献
7.
In the molten salt environment, the BaTiO3 spherical nanoparticles (BTNPs) and BaTiO3 nanorods (BTNRs) have been synthesized, respectively, in which spherical TiO2 and rod-like BaTi2O5 are precursors. The dissolution–precipitation is the main dominated mechanism in the formation of BTNPs, while the dissolution–diffusion is the main mechanism responsible for the formation of BTNRs. The latter is also called as topochemical mechanism, which is associated with the assembly of [TiO6] octahedron units in the transformation from BaTi2O5 to BaTiO3. By using these two kinds of BT as fillers, polyvinylidene fluoride (PVDF)-based composites, BTNPs/PVDF and BTNRs/PVDF, have been constructed and their dielectric properties have been investigated. It was found that there were three main factors related to filler morphology affecting the dielectric properties of the composites, i.e., intrinsic polarization of filler, the interface polarization and electric field distribution between the filler and the matrix. Though the spontaneous polarization of 600-nm-sized BTNPs is larger, the interfacial area of BTNRs/PVDF composite is larger than that of BTNPs (600 nm)/PVDF composite, which is advantageous to enhance the interface polarization. Moreover, the analysis through Potential-Across model revealed that BTNRs/PVDF composite has stronger electric field intensity distribution across BTNRs filler in comparison with BTNPs/PVDF, which plays the key role in improving the dielectric properties of composites. This work not only presents the BTNRs/PVDF composite with good dielectric performance, the related design and the theory analysis also facilitate the development of more new high dielectric composites based on morphology control of ferroelectric filler. 相似文献
8.
Polycrystalline sample of Pb2Sb3LaTi5O18, a member of tungsten- bronze (TB family, was prepared using a high temperature solid- state reaction technique. XRD analysis
indicated the formation of a single-phase orthorhombic structure. The dielectric studies revealed the diffuse phase transition
and the transition temperature was found to be at 52° C. Impedance plots were used as tools to analyse the sample behaviour
as a function of frequency. Cole-Cole plots showed Debye relaxation. The activation energy was estimated to be 0·634 eV from
the temperature variation of d.c. conductivity. The nature of variation of d.c. conductivity with temperature suggested NTCR
behaviour. 相似文献
9.
Chunchun Li Wangxi Wen Huaicheng Xiang Liang Fang Yihua Sun 《Journal of Materials Science: Materials in Electronics》2018,29(3):1907-1913
Crystal structure and dielectric properties of Zn3Mo2O9 ceramics prepared through a conventional solid-state reaction method were characterized. XRD and Raman analysis revealed that the Zn3Mo2O9 crystallized in a monoclinic crystal structure and reminded stable up to1020 °C. Dense ceramics with high relative density (~ 92.3%) were obtained when sintered at 1000 °C and possessed good microwave dielectric properties with a relative permittivity (ε r ) of 8.7, a quality factor (Q?×?f) of 23,400 GHz, and a negative temperature coefficient of resonance frequency (τ f ) of around ??79 ppm/°C. With 5 wt% B2O3 addition, the sintering temperature of Zn3Mo2O9 ceramic was successfully lowered to 900 °C and microwave dielectric properties with ε r ?=?11.8, Q?×?f?=?20,000 GHz, and τ f = ??79.5 ppm/°C were achieved. 相似文献
10.
A new member of lead-free piezoelectric ceramics of the BNT-based group, (1 − x)Bi0·5Na0·5TiO3−x
BaNb2O6, was prepared by conventional solid state reaction and its dielectric properties and relaxation was investigated. X-ray diffraction
showed that BaNb2O6 diffused into the lattice of Bi0·5Na0·5TiO3 to form a solid solution with perovskite-type structure. A diffuse character was proved by the linear fitting of the modified
Curie-Weiss law. The temperature dependence of dielectric constant at different frequencies revealed that the solid solution
exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with x = 0·002 and 0·006 exhibited obvious relaxor characteristics near the low temperature dielectric abnormal peak, T
f, and the samples with x = 0·010 and 0·014 exhibited obvious relaxor characteristics between room temperature and T
f. The mechanism of relaxor behaviour was also discussed according to the macro-domain to micro-domain transition theory. 相似文献
11.
V. M. Manisha K. P. Murali S. N. Potty V. Priyadarsini R. Ratheesh 《Bulletin of Materials Science》2004,27(2):149-153
MXTi7O16 (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric
properties such as dielectric constant (εr), loss tangent (tan δ) and temperature variation of dielectric constant (τεr) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have
relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials
has been examined using X-ray diffraction studies and microstructure using SEM method. 相似文献
12.
Piezoelectric powders and ceramics with the composition of Pb0.95Sr0.05(Zr0.52Ti0.48)O3–Pb(Zn1/3Nb2/3)O3–Pb(Mn1/3Sb2/3)O3 (PZT–PZN–PMS) were prepared by molten salt synthesis (MSS) and conventional mixed-oxide (CMO) methods, respectively. The influence of synthesis process on the properties of powders and ceramics were investigated in detail. The results show that the MSS method significantly improved the sinterability of PZT–PZN–PMS ceramics, resulting in an improvement of dielectric and piezoelectric properties compared to the CMO method. The optimum values of MSS samples are as follows: r = 1773; tan δ = 0.0040; Tc = 280 °C; d33 = 455 pC/N; kp = 0.70; Qm = 888; Ec = 10.3 kV/cm; and Pr = 28.2 μC/cm2, at calcination of 800 °C and sintering of 1120 °C temperature. 相似文献
13.
Wang-Suo Xia Fei Jin Mei Wang Xin Wang Guo-Ying Zhang Li-Wei Shi 《Journal of Materials Science: Materials in Electronics》2016,27(2):1100-1104
ZnTa2O6 ceramics with various amount of Al2O3 additive were synthesized by a conventional mixed-oxide route. The grain growth of ZnTa2O6 ceramics was accelerated with Al2O3 additive. However, excessive addition (>1.0 wt%) of Al2O3 leaded to abnormal grain growth. With Al2O3 addition, the Al2O3 additive did not solubilized into ZnTa2O6 structure but resulted in forming the second phase. The Al2O3 addition resulted in the lower sintering temperature of ZnTa2O6 ceramics and improved microwave dielectric properties. The dielectric constant (εr) of the samples did not change much and ranged from 32.41 to 34.33 with different amount of Al2O3 addition. The optimized quality factor (Q × f) was higher than 70,000 GHz as a result of the denser ceramics. The temperature coefficient of resonant frequency (τ f ) of the doped ZnTa2O6 ceramics could be optimized to near-zero. 相似文献
14.
Nanosized Ag2V4O11 powders have been prepared via the low-temperature molten salt method using LiNO3 as a reaction medium. The powders have been characterized by x-ray diffraction and transmission electron microscopy. The discharge properties of the powders have been assessed by the galvanostatic discharge test using CR2016 coin cells. The powder made at 300°C for 2 h is composed of nearly spherical particles about 40 nm in size. The discharge test shows that the powders prepared by the low-temperature molten salt method exhibit high discharge capacities. 相似文献
15.
Huanfu Zhou Wendong Sun Jin Huang Kangguo Wang Xiuli Chen Xiaobin Liu Hong Ruan 《Journal of Materials Science: Materials in Electronics》2018,29(8):6232-6235
In the present work, a novel MgAl2Ti3O10 ceramic was obtained using a traditional solid-state reaction method. X-ray diffraction and energy dispersive spectrometer showed that the main MgAl2Ti3O10 phase was formed after sintered at 1300–1450 °C. With rising the sintering temperature from 1300 to 1450 °C, the bulk density (ρ), relative permittivity (ε r ) and Q?×?f value firstly increased, reached the maximum values (3.61 g/cm3, 14.9, and 26,450 GHz) and then decreased. The temperature coefficient of resonator frequency (τ f ) showed a slight change at a negative range of ??94.6 to ??83.7 ppm/°C. When the sintering temperature was 1400 °C, MgAl2Ti3O10 ceramics exhibited the best microwave dielectric properties with Q?×?f?=?26,450 GHz, ε r ?=?14.9 and τ f ?=???83.7 ppm/°C. 相似文献
16.
Dong-Xiang Zhou Fei Sun Yun-Xiang Hu Qiu-Yun Fu Gang Dou 《Journal of Materials Science: Materials in Electronics》2012,23(5):981-989
The Mg3B2O6 ceramics with lithium magnesium zinc borosilicate (LMZBS) glass were prepared at a lower sintering temperature. The effects of the glass addition on the densification, phase development, microstructure and microwave dielectric properties of the Mg3B2O6 ceramics were investigated. The addition of LMZBS glass improved the densification and lowered the sintering temperature of Mg3B2O6 ceramics from 1,300 to 950 °C. X-ray diffraction patterns showed that Mg3B2O6 transformed into Mg2B2O5 and a new phase, Li2ZnSiO4, crystallized from the glass phase. Because of the high dielectric performance of these phases, Mg3B2O6 mixed with 55 wt% LMZBS sintered at 950 °C for 3 h had εr = 6.8, Q × f = 50,000 GHz, and τf = ?64 ppm/°C at 7.28 GHz. The chemical compatibility of ceramic-glass composites with Ag was also investigated for LTCC. 相似文献
17.
Empirical calculational approaches have been used to evaluate the enthalpy, entropy, heat capacity, and melting point of iron(II) niobate and iron(II) tantalate and the coefficients A, B, and C in an equation for the temperature dependence of their heat capacity. The melting point of FeTa2O6 has been experimentally determined to be 1891 ± 5 K. The calculated heat capacity (C°p (298.15 K)) of iron tantalate and the Gibbs energies of formation of FeN2O6 and FeTa2O6 have been compared to previously reported data. 相似文献
18.
Bin Tang Moke Zhou Yingxiang Li Fei Wang Shuren Zhang 《Journal of Materials Science: Materials in Electronics》2018,29(23):19791-19797
In recent reports, the microwave dielectric properties of Li2ZnTi3O8 ceramic deviate largely from the optimal value. In this paper by the Rietveld refinement method, the co-existence of the secondary phases is confirmed which is due to the zinc volatilization. Thus, the excessive ZnO addition is introduced to obtain a high purity Li2ZnTi3O8 phase. Microwave dielectric properties are theoretically calculated to prove the above statement, based on the property indices of these phases. The calculated result is consistent to the measured data, with relative deviation around 5%. The optimized properties make the ceramic a promising ceramic candidate for the microwave applications. 相似文献
19.
S. S. Redozubov N. F. Kartenko I. M. Gaidamaka E. A. Nenasheva 《Inorganic Materials》2016,52(11):1166-1171
Ceramic samples based on ZnTa2O6 and ZnTa2O6–MO2 (M = Ti, Zr) systems have been obtained by the solid state ceramic route. The phase composition and microstructure of samples were investigated. The effect of the aliovalent substitution of ions Zn2+ and Ta5+ by M4+ (M = Ti, Zr) in the structure of ZnTa2O6 on microwave dielectric properties of ceramics was studied. The way of the compensation of the positive temperature coefficient of resonant frequency of dielectric resonators based on ZnTa2O6 ceramics with using the aliovalent substitution of cations was proposed. Dielectric resonators with the high temperature stability of the resonant frequency and high dielectric properties in the microwave range based on the ZnTa2O6–ZrO2 system were obtained for application in electronics. 相似文献