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1.
The sintering behavior, microstructure and microwave dielectric properties of Mg4(Nb2?x Sb x )O9 (0?≤?x?≤?2) solid solutions were investigated systematically by X-ray diffraction(XRD), scanning electron microscopy(SEM) and a network analyzer. The solid solutions of Mg4(Nb2?x Sb x )O9 was formed with x value being no more than 1.6. The dielectric constant (?) of the sintered ceramics decreased from 13.06 to 6.28 with Sb content x from 0 to 1.6. With a substitution of Sb5+ for Nb5+ (0.04?≤?x?≤?0.08), the sintering temperature of Mg4Nb2O9 ceramics was decreased from 1400 to 1300 °C without degradation of the Qf values. The optimum microwave dielectric properties of ??~?12.26, Qf?~?168,450 GHz, and τ f?~??56.4 ppm/°C were obtained in the composition of Mg4(Nb1.6Sb0.4)O9 sintered at 1300 °C. 相似文献
2.
Mg4Nb2O9 ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg4Nb2O9 were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q×f o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. τ f value of ?17.1 ppm/°C was improved by the addition of TiO2 and τ f value of 6.7 ppm/°C was obtained at 20 wt% TiO2. Chemical compatibility of Mg4Nb2O9 with Ag was tested to identity the possibility of using Mg4Nb2O9 for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg4Nb2O9 and Ag powder heat treated at 900°C, it was considered that the Mg4Nb2O9 system is applicable to the multilayer microwave devices using Ag as an electrode. 相似文献
3.
Jong-Bong Lim Sahn Nahm Hyo-Tae Kim Jong-Hee Kim Jong-Hoo Paik Hwack-Joo Lee 《Journal of Electroceramics》2006,17(2-4):393-397
The effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of BaTi4O9 ceramics was investigated. The BaTi4O9 ceramics were able to be sintered at 975∘C when B2O3 was added. This decrease in the sintering temperature of the BaTi4O9 ceramics upon the addition of B2O3 is attributed to the formation of BaB2O4 second phase whose melting temperature is around 900∘C. The B2O3 added BaTi4O9 ceramics alone were not sintered below 975∘C, but were sintered at 875∘C when CuO was added. The formation of BaCu(B2O5) second phase could be responsible for the decrease in the sintering temperature of the CuO and B2O3 added BaTi4O9 ceramics. The BaTi4O9 ceramics containing 2.0 mol% B2O3 and 5.0 mol% CuO sintered at 900∘C for 2 h have good microwave dielectric properties of εr = 36.3, Q× f = 30,500 GHz and τf = 28.1 ppm/∘C 相似文献
4.
R. K. Bhuyan T. Santhosh Kumar D. Goswami A. R. James D. Pamu 《Journal of Electroceramics》2013,31(1-2):48-54
Dielectric ceramics of Mg2TiO4 (MTO) were prepared by solid-state reaction method with 0.5–1.5 wt.% of La2O3 or V2O5 as sintering aid. The influences of La2O3 and V2O5 additives on the densification, microstructure and microwave dielectric properties of MTO ceramics were investigated. It is found that La2O3 and V2O5 additives lowered the sintering temperature of MTO ceramics to 1300 °C and 1250 °C respectively, whereas the pure MTO exhibits highest density at 1400 °C. The reduction in sintering temperature with these additives was attributed to the liquid phase effect. The average grain sizes of the MTO ceramics added with La2O3, and V2O5 found to decrease with an increase in wt%. The dielectric constant (εr) was not significantly changed, while unloaded Q values were affected with these additives, and the values were in the range of 92,000–157,550 GHz and 98,000–168,000 GHz with the addition of La2O3 and V2O5, respectively. The dielectric properties are strongly dependent on the densification and the microstructure of the MTO ceramics. The decrease in Q×f o value at higher concentration of La2O3 and V2O5 addition was owing to inhomogeneous grain growth and the liquid phase which is segregated at the grain boundary. In comparison with pure MTO ceramics, La2O3 and V2O5 additives effectively improved the densification and dielectric properties with lowering of sintering temperature. The proposed loss mechanisms suggest that the oxygen vacancies and the average grain sizes are the influencing factors in the dielectric loss of MTO ceramics. 相似文献
5.
Zhenxing Yue Jing Yan Fei Zhao Zhilun Gui Longtu Li 《Journal of Electroceramics》2008,21(1-4):141-144
The low-temperature sintered microwave dielectric ceramics with composition of ZnTiO3-0.25TiO2 were prepared by adding a small amount of low-melting compounds CuO-V2O5-Bi2O3 (CVB). The phase relationship and dielectric properties as a function of sintering temperature and the additional amount were studied. It is demonstrated that the addition of low-melting CVB can suppress the formation of Zn2TiO4 at low temperature, but decrease the decomposition temperature of ZnTiO3. The sintering temperature has a significant effect on the stability of ZnTiO3 and dielectric properties of sintered ceramics. CVB addition can promote the densification of ceramics through liquid-phase sintering. The dense 2wt% CVB-doped ZnTiO3-0.25TiO2 ceramics prepared at 850 °C have excellent dielectric properties of ??=?30, Q×f?=?32,000 GHz, and τ f ?=?+12 ppm/ °C. 相似文献
6.
Pinyang Fang Huiqing Fan Laijun Liu Jin Chen Shaojun Qiu 《Journal of Electroceramics》2009,23(1):52-55
Ferroelectric ceramics, SrBi2Nb2O9 (SBN), Sr0.8Cu0.2Bi2Nb2O9 (SCBN) and Sr0.8K0.1Na0.1Bi2Nb2O9 (SKNBN) were prepared by a solid state reaction process. X-ray diffraction analysis shows that the alkali and Cu almost diffuse
into the SBN lattice to form a solid solution during sintering and some slight secondary phases was detected. The effect of
alkali and Cu on dielectric properties of the SBN ceramics was discussed. The dielectric loss factor of (K,Na) doped SBN ceramics
degraded considerably to 0.01 and their frequency and temperature stabilities were enhanced. The dielectric constant was enhanced
by approximately 60% and the Curie temperature (Tc) was also improved for Cu doped SrBi2Nb2O9 ceramics. 相似文献
7.
Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with B2O3 and CuO additions 总被引:1,自引:0,他引:1
Jeong-Ryeol Kim Dong-Wan Kim Sung Hun Yoon Kug Sun Hong 《Journal of Electroceramics》2006,17(2-4):439-443
The low sintering temperature and the good dielectric properties such as high dielectric constant (ε
r
), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components
in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric
properties of Ba3Ti5Nb6O28 ceramics were investigated as a function of B2O3-CuO content. The pure Ba3Ti5Nb6O28 system showed a high sintering temperature (1250∘C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε
r
of 37, TCF of −12 ppm/∘C. The addition of B2O3-CuO was revealed to lower the sintering temperature of Ba3Ti5Nb6O28, 900∘C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε
r
of 40, TCF of 9 ppm/∘C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained
in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties. 相似文献
8.
Monazite-type compounds, BiPO4 polymorphs were prepared by the solid-state reaction method. The phase transformation and microwave dielectric properties
of sintered ceramics were investigated using the X-ray powder diffraction (XRD) and a network analyzer, respectively. The
low-temperature phase of BiPO4 has monoclinic structure, and was transformed into the high-temperature phase with a slight distortion of monoclinic when
it is heated above 600∘C. The effect of the transformation on the microwave dielectric properties was examined. It was found that the dielectric
properties of each phase were significantly different. In particular, the high-temperature phase sintered at 950∘C has good microwave dielectric properties; the relative dielectric constant (ε
r
) = 22, the quality factor (Q× f) = 32,500 GHz and the temperature coefficient of resonant frequency (τ
f
) = − 79 ppm/ ∘C. 相似文献
9.
Polycrystalline Ba(FeNb)0.5O3/BFN ceramics were sintered conventionally and in a microwave (MW) furnace, respectively. Conventional and microwave sintering temperatures were same with different soaking times. Microwave sintering of BFN ceramics showed enhanced grain growth with improved dielectric properties. Highest dielectric constant (~29,913 at 1 kHz) at room temperature (RT) was observed in BFN ceramics sintered in MW furnace for 30 min. At RT, a non-Debye type of dielectric relaxation was observed in both conventionally and MW sintered BFN ceramics. The observed giant dielectric constant of conventionally and MW sintered BFN ceramics was attributed to intrinsic (space charge polarization) and extrinsic (Maxwell-Wagner type polarization) effects, respectively. 相似文献
10.
The nanocrystals of CaCu3Ti4O12 ceramic were prepared by microwave flash combustion technique. The microwave sintering of powders was optimized to 1025 − 1075 °C for 20 min with heating and cooling rate of 50 °C/min. Microstructural evaluation of sintered sample was carried out using SEM. The dielectric properties were measured in the frequency range 10–2 × 106 Hz and the temperature range 30–100 °C. The CCTO sample sintered at 1075 °C had giant dielectric constant 53,300 at 100 Hz. It was observed that dielectric constant was greatly increased on a slight increase in sintering temperature. Modulus and impedance analysis were performed to explore the observed unusual dielectric response. Grain and grain boundary resistance were observed as 8 Ω and 350,000 Ω, respectively. The grain boundary activation energy for electro-conduction was calculated as 0.65 eV by using the characteristic frequencies in cole-cole plots. It was noticed that the thermally activated charge carriers had long-range mobility. 相似文献
11.
In multiplayer passive devices, low sintering temperature dielectric materials were needed to co-fire with low melting point inner electrode such as copper or silver, a major problem of base metal electrode (BME) was that the devices must be fired under low oxygen partial pressure atmosphere to protect Cu from oxidation. In this paper, dielectric properties of Bi(VxNb1?x)O4 (x?=?0.001, 0.004, 0.008, 0.016, 0.048) microwave ceramics sintered under air and N2 atmosphere have been investigated. The densification temperature sintered in different atmosphere decreased from 1010 to 830°C with the amount of V2O5 increasing from 0.001 to 0.048. Due to the increasing vacancy defects, the density of ceramics sintered in N2 was smaller than that sintered in air. The ceramics sintered under N2 have similar dielectric constant, and its Qf values are higher while x?<?0.016. 相似文献
12.
The structural and microwave dielectric properties of Ba5?x La x Ti x Nb4?x O15 (1?≤?x?≤?3) was investigated. The single phase with A5B4O15-type cation-deficient hexagonal perovskite structure was obtained over the whole composition range. These ceramics have high dielectric constant up to 56, high quality factors (Q?×?f ) up to 35,000, and low temperature coefficient of resonant frequencies (τ f ) in the range +69 to ?3 ppm °C?1. The dielectric constants and τ f of these ceramics gradually decrease parallel to an increase in B-site bond valence with increasing La and Ti content. 相似文献
13.
The effect of V2O5 substitution on the sintering behavior and the microwave dielectric properties of BiNbO4 ceramics were studied. The sintering temperatures of Bi(V x Nb1?x )O4 ceramics decrease from 990 to 810°C with x value increasing from 0.002 to 0.064. The size of grains increased with the sintering temperature increasing and decreased with the substitution amount increasing. The dielectric properties are affected by the microstructures very much. The quality factor Q value is from 2500 to 4000 at about frequency?=?5 GHz and reach to the maximum when x?=?0.032. With the different x value, the Q f values change between 15000 to 20000 GHz; the τ f values changes between 0 and +20 ppm/°C between temperature range 25~85°C and decreased with the increasing of x value. 相似文献
14.
15.
16.
Chien-Min Cheng Ying-Chung Chen Cheng-Fu Yang Chao-Chin Chan 《Journal of Electroceramics》2007,18(1-2):155-160
1,500 °C−sintered MgTa2O6 ceramic exhibits microwave dielectric characteristics of ɛ
r = 30.5, Q × f = 56,900 GHz, and τ
f = 28.3 ppm/°C, whereas 1,400 °C-sintered MgNb2O6 ceramic exhibits microwave dielectric characteristics of ɛ
r = 21.7, Q × f = 89,900 GHz, and τ
f = −68.5 ppm/°C. In order to find the dielectric resonators with τ
f value close to 0 ppm/°C, the effects of sintering condition and composition on the microwave dielectric characteristics of
Mg(Ta1−x
Nb
x
)2O6 ceramics (0.25 ≦ x ≦ 0.35) prepared under sintering temperature of 1,300–1,450 °C are investigated. The results show that as the sintering temperature
increases from 1,300 to 1,450 °C, the ɛ
r, Q × f and τ
f values of Mg(Ta1−x
Nb
x
)2O6 ceramics all increase and saturate at 1,450 °C. On the other hand, as the Nb2O5 content decreases, the τ
f values of Mg(Ta1−x
Nb
x
)2O6 ceramics will shift to near 0 ppm/°C. The optimized sintering conditions and composition to obtain the Mg(Ta1−x
Nb
x
)2O6 dielectrics with τ
f close to 0 ppm/°C are sintering temperature of 1,450 °C, sintering duration of 4 h, and composition of x = 0.25, which exhibits the microwave dielectric characteristics of ɛ
r = 27.9, Q × f = 33,100 GHz, and τ
f = −0.7 ppm/°C. 相似文献
17.
J. G. Noudem M. Prevel A. Veres D. Chateigner J. Galy 《Journal of Electroceramics》2009,22(1-3):91-97
Hole-doped Ca3Co4O9 (Co349) ceramics were prepared using solid-state reaction. Two processing strategies have been used to produce the thermoelectric oxide ceramics, Conventional and Spark Plasma (SPS) Sintering to control the grains consolidation, texturation and sample densification. Thermoelectric properties were measured and the influence of the processing conditions on the properties was evidenced. SPS favours shorter elaboration times and produces samples with larger thermoelectric properties due to better densification and alignment. The effect of the free deformation and texturation using the SPS technique is discussed. Seebeck coefficient values of 180 μV/K at 873 K are obtained. 相似文献
18.
Chi-Ben Chang Keh-Chyang Leou Wen-Yang Shu I-Nan Lin 《Journal of Electroceramics》2007,18(1-2):167-173
Effect of SnO2 addition on the crystal structure/microstructure and the related microwave dielectric properties of the Ba2Ti9O20 were systematically investigated. Incorporation of SnO2 markedly stabilized the phase constituent and microstructure for the Ba2Ti9O20 such that high quality materials can be obtained in a much wider processing window. The sintered density of the Ba2Ti9O20 increased linearly, but the microwave dielectric constant (K) decreased monotonically, with the SnO2 doping concentration. The quality factor (Qxf) of the materials increased firstly due to the addition of SnO2, but decreased slightly with further increase in SnO2 content. The best microwave dielectric properties obtained are K = 38.5 and Qxf = 31,500 GHz, which occurs for the 0.055 mol SnO2-doped and 1350 °C/4 h sintered samples. These properties are markedly better than those for undoped materials (K = 38.8 and Qxf = 26,500 GHz). 相似文献
19.
Li2MgTiO4 (LMT) ceramics which are synthesized using a conventional solid-state reaction route. The LMT ceramic sintered at 1250°C for 4 h had good microwave dielectric properties. However, this sintering temperature is too high to meet the requirement of low-temperature co-fired ceramics (LTCC). In this study, the effects of B2O3 additives and sintering temperature on the microstructure and microwave dielectric properties of LMT ceramics were investigated. The B2O3 additive forms a liquid phase during sintering, which decreases the sintering temperature from 1250°C to 925°C. The LMT ceramic with 8 wt% B2O3 sintered at 925°C for 4 h was found to exhibit optimum microwave dielectric properties: dielectric constant 15.16, quality factor 64,164 GHz, and temperature coefficient of resonant frequency -28.07 ppm/°C. Moreover, co-firing of the LMT ceramic with 8 wt% B2O3 and 20 wt% Ag powder demonstrated good chemical compatibility. Therefore, the LMT ceramics with 8 wt% B2O3 sintered at 925°C for 4 h is suitable for LTCC applications. 相似文献
20.
Lidmila Burianova Stanislav Panos Martin C. Stennett Anthony R. West Ganesanpotti Subodh Mailadil T. Sebastian Stanislav Kamba 《Journal of Electroceramics》2010,25(2-4):116-121
In this paper, measurements of the nonlinear ferroelectric, piezoelectric and dielectric properties of Pb9Ce2Ti12O36 (Pb9CTO) and Ba2NdTi2Nb3O15 (BNTN) ferroelectric ceramics are presented. Hysteresis P(E) loops were measured as a function of applied electric field, frequency and temperature. The coercive field (E c) and remnant polarization (P r) displayed temperature and frequency dependence. Lead-free BNTN ceramics exhibited a coercive field E c?>?2.4 kV mm?1 and a piezoelectric coefficient d 33?=?2 pC N?1. The hysteresis loop was pinched above 110°C and a linear response was observed at 155°C, typical of a paraelectric material. Pb9CTO was shown to be ferroelectric with coercive field E c?=?1.2 kV mm?1 and a d 33?=?65 pC N?1. The frequency dependences of the impedance of the Pb9CTO discs were analyzed. 相似文献