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1.
Pian Pian Ma Lei Yi Xiao Qiang Liu Lei Li Xiang Ming Chen 《Journal of the American Ceramic Society》2013,96(6):1795-1800
Effects of Mg substitution on order/disorder transition, microstructure, and microwave dielectric characteristics of Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics have been investigated. The ordered complex perovskite solid solutions are obtained in Ba((Co0.6?x/2Zn0.4?x/2Mgx)1/3Nb2/3)O3 ceramics (x = 0, 0.1, 0.2, and 0.3), and the ordering degree in the as‐sintered dense ceramics increases with increasing Mg‐substitution amount. The significantly improved Qf value is obtained in the present ceramics with increasing x, whereas the dielectric constant decreases slightly together with some increase of temperature coefficient of resonant frequency. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3: εr = 33.7, Qf = 93 800 GHz, and τf = 9.6 ppm/°C. In the Mg‐substituted compositions, clear domain boundaries are obtained and the domain size increases as x increases, the highest Qf value is obtained when the domain size is about 40–60 nm in the ceramics with x = 0.3. The increased ordering degree and the fine ordering domain structure are considered to primarily contribute to the significant increase of Qf value in the Mg‐substituted Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics. 相似文献
2.
Microwave Dielectric Properties and Thermally Stimulated Depolarization Currents of (1−x)Ba(Mg1/3Nb2/3)O3–xBaSnO3 Solid Solutions
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Jie Zhang Yuanyuan Zhou Zhenxing Yue Xiaohua Zhang Longtu Li 《Journal of the American Ceramic Society》2015,98(12):3942-3947
Microwave dielectric ceramics of (1?x)Ba(Mg1/3Nb2/3)O3‐xBaSnO3 [(1?x)BMN‐xBS] with high quality factors was synthesized by the solid‐state reaction method. The effects of BaSnO3 additions (x = 0–0.2) on the sinterability, crystal structures, microwave dielectric properties, and microwave dielectric loss mechanisms of BMN were investigated systematically. The degree of 1:2 cation ordering was decreased with increasing Sn content and eventually faded away as x ≥ 0.1, where the low‐temperature relaxations disappeared coincidently through the thermally stimulated depolarization current technique. It was supposed to be the short‐range misplacements of the B‐site cations within the long‐range ordered structure. Meanwhile, the high‐temperature relaxations associated with the in‐grain oxygen vacancies were found in all the title compounds. Though the concentrations of oxygen vacancies of 0.8BMN‐0.2BS were higher than BMN, high Q × f values could also be obtained even in the absence of 1:2 cation ordering. Specifically, the excellent characteristics like εr = 29.02, Q × f = 90 000 GHz and τf = 6.3 ppm/°C were achieved in the specimens of x = 0.2 sintered at 1450°C. 相似文献
3.
Song Lin Zhang Pian Pian Ma Xiao Qiang Liu Xiang Ming Chen 《Journal of the American Ceramic Society》2015,98(10):3185-3191
The microwave dielectric characteristics of Ca[(Ga1/2Nb1/2)1?xTix]O3 ceramics were investigated together with the structure evolution. The excellent microwave dielectric characteristics were achieved by forming solid solution between Ca(Ga1/2Nb1/2)O3 and CaTiO3 in the present ceramics. The solid solutions in space group Pbnm with antiphase and inphase tilting were determined for all compositions where minor secondary phase was detected for x = 0–0.47, whereas no B‐site ordering was detected. Owing to the structural modification, the dielectric constant (εr) increased with increasing x, and the temperature coefficient of resonant frequency (τf) could be tuned from negative to positive, while the decrease of Qf value was acceptable. The best combination of microwave dielectric properties was obtained at x = 0.47: εr = 51.6, Qf = 34 100 GHz and τf = ?0.3 ppm/°C. 相似文献
4.
Microstructures and Microwave Dielectric Properties of Ba((Co0.55Zn0.35Mg0.1)1/3Nb2/3)O3‐BaZrO3 Ceramics
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Pian Pian Ma Lei Yi Shu Ya Wu Xiang Ming Chen Hui Gu 《Journal of the American Ceramic Society》2015,98(2):520-527
Microstructures and microwave dielectric properties of (1?x)Ba((Co0.55Zn0.35Mg0.1)1/3 Nb2/3)O3‐xBaZrO3 (x = 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06) ceramics have been investigated. The 1:2 ordered structure remains in the solid solutions when x is less than 0.03, but the ordering is destabilized. While, the local ordering behavior, which generates from compositional inhomogeneous, is observed in the composition with x = 0.04, where the 1:1 ordered phase begins to form. For x = 0.05 and 0.06, the solid solutions are comprised of nanometer‐sized 1:1 and 1:2 ordered domains, those are dispersed in a disordered matrix. The lower Qf values of the as‐sintered ceramics mainly because of the lower ordering degrees. BaZrO3 substitution decreases both the annealing time and temperature. The effects of annealing process upon the improvement of Qf values are significant for the lower substitution levels (x = 0.01 and 0.02), while only slight effects are determined for high substitution levels (x = 0.04, 0.05, and 0.06). The highest Qf value of 84,500 GHz is obtained for 1 mol% BaZrO3 substituted composition, after annealing at 1300°C for 8 h. 相似文献
5.
Rui Ze Guo Rui Da Shi Xiao Li Zhu Xiang Ming Chen 《Journal of the American Ceramic Society》2023,106(7):4275-4283
The ordered domain engineering was investigated for Ba[(Zn0.8Mg0.2)1/3Nb2/3]O3 microwave dielectric ceramics to synergistically modify the physical properties especially the temperature coefficient of resonant frequency τf and quality factor Q value together with the thermal conductivity. The ordered domain structure could be tailored and controlled by the post-densification annealing, and the fine ordered domain structures with high ordering degree and low-energy domain boundary were obtained in the present ceramics annealed around 1400°C for 24 h, where the Qf value was improved from 51 000 to 118 000 GHz, τf was suppressed from 30 to 25.5 ppm/°C. Moreover, the thermal conductivity at room temperature was increased from 3.79 to 4.30 W m−1 K−1, and the Young's modulus was improved from 98 to 214 GPa. The present work provided a promising approach for synergistic modification of physical properties in Ba-based complex perovskite microwave dielectric ceramics. 相似文献
6.
Sr(Ga0.5Nb0.5)1−xTixO3 Low‐Loss Microwave Dielectric Ceramics with Medium Dielectric Constant
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Pian Pian Ma Xiao Qiang Liu Fa Qiang Zhang Juan Juan Xing Xiang Ming Chen 《Journal of the American Ceramic Society》2015,98(8):2534-2540
The microwave dielectric properties of Sr(Ga0.5Nb0.5)1?xTixO3 (x = 0, 0.1, 0.2 and 0.3) ceramics have been investigated together with their microstructures. Single‐phase solid solutions are achieved in this series of ceramics. The ordering features are comprehensively analyzed by transmission electron microscopy and Raman spectroscopy. Local 1:1 ordering in B‐site leads to a double‐cubic structure with space group , while Ti substitution disrupts this 1:1 ordering between Ga and Nb, and the metastable ordering between Ti and (Ga + Nb) is speculated to form due to their large size difference. The dielectric constant and temperature coefficient of resonant frequency increase nonlinearly as x increases, while the Qf value decreases gradually. The variation trend of Qf value is mainly attributed to the intrinsic loss because of the increasing vibrational anharmonicity by Ti substitution. The ordering transition from short coherence, long‐range ordering to short‐range ordering with increasing Ti content has an agreeable and weak effect on the Qf value. The best combination of microwave dielectric properties is achieved for the composition of x = 0.3: εr = 46.6, Qf = 42 200 GHz and τf = 5.0 ppm/°C. 相似文献
7.
A/B site co-substituted (Ca1?0.3xLa0.2x)[(Mg1/3Ta2/3)1?xTix]O3 ceramics (0.1 ≤ x ≤ 0.5) were prepared by solid state reaction and the structures, microstructures and dielectric properties were investigated. B site 1:2 cation ordering and oxygen octahedra tilting lead to monoclinic symmetry with space group P21/c for x = 0.1. For x above 0.1, the ordering was destroyed and the crystal structure became orthorhombic with space group Pbnm. The B site 1:2 cation ordering tended to be destroyed to form 1:1 ordering by the A site La3+ substitution. The dielectric constant increased linearly with increasing content of Ti4+ as the increasing second Jahn–Teller distortion enhanced the B site cation rattling. The temperature coefficient of resonant frequency and Qf values showed abnormal variations, which were refined to be caused by the increasing A site cation vacancy and diffused distribution of small size ordering domains respectively. Good combination of microwave dielectric properties was obtained at x = 0.5, where ?r = 48, Qf = 21,000 GHz and τf = 2.2 ppm/°C. 相似文献
8.
Zhi Hua Kang Rui Ze Guo Rui Da Shi Xiao Li Zhu Xiang Ming Chen 《Journal of the American Ceramic Society》2023,106(6):3471-3480
It is an important subject to improve the temperature coefficient of resonant frequency (τf) and thermal conductivity (κ) of microwave dielectric ceramics without reducing the Qf value. Ordered domain engineering was applied to realize the previous objectives in Ba(Mg1/3Ta2/3)O3 ceramics. With the increasing ordering degree from 0.835 to 0.897, the optimized Qf value was obtained. Meanwhile, near zero τf from 11.9 to 5.6 ppm °C−1 was achieved, together with increased κ from 5.5 to 7.6 W m−1 K−1, and enhanced dielectric strength from 801 to 921 kV cm−1. The noticeable ordered domain structure with large ordered domains (∼100 nm) and low-energy domain boundaries was revealed in Ba(Mg1/3Ta2/3)O3. The consequent weakened phonon scattering rises the thermal conductivity. The increased bond covalency and oxygen distortion in ceramics with higher ordering degree were suggested as a cause of enlarged bandgap, which enhanced the dielectric strength. The reduced τf is dominated by the less “rattling” space of the cations in the ordered state by inducing more positive τε. The reduced τf, optimized thermal conductivity, and Qf value in the present work indicate that the ordered domain engineering could open up a new direction for the optimization of microwave dielectric ceramics. 相似文献
9.
Structure and microwave dielectric properties of the Li2/3(1−x)Sn1/3(1−x)MgxO systems (x = 0‐4/7)
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Zixuan Fang Bin Tang Ying Yuan Xing Zhang Shuren Zhang 《Journal of the American Ceramic Society》2018,101(1):252-264
In this paper, the Li2/3(1?x)Sn1/3(1?x)MgxO (LSMxO) ceramic systems were prepared by solid‐state reaction using novel atmosphere‐controlled sintering (x = 0‐4/7). Pure Li2SnO3 was observed for x = 0, the Li2Mg3SnO6 and Li2SnO3 coexisted for x = 1/7, and the coexistence of three kinds of phases was detected for x = 1/5 and 1/4, including Li4MgSn2O7 impurity phase. Pure Li2Mg3SnO6‐like phase with cubic rock salt structure in Fm‐3m space group was obtained in the range of 1/3‐4/7. All samples showed well‐dense and smooth microstructures. The microwave dielectric properties highly depended on the phase composition, bond valence, FWHM of Raman spectrum, Raman shift, average grain sizes, and octahedral distortion. The LSMxO ceramics sintered at 1250°C for 5 hours possessed excellent comprehensive properties of εr = 15.43, Q×f = 80 902 GHz and τf = +5.61 ppm/°C for x = 1/7. Typically, the LSMxO ceramics sintered at 1350°C for 5 hours showed a maximum Q × f of 168 330 GHz for x = 1/2. 相似文献
10.
Effect of Ordering on the Microwave Dielectric Properties of Spinel‐Structured (Zn1−x(Li2/3Ti1/3)x)2TiO4 Ceramics
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Spinel‐structured (Zn1?x(Li2/3Ti1/3)x)2TiO4 (x = 0–1) microwave dielectric ceramics were manufactured via a conventional mixed‐oxide method. The X‐ray diffraction and Raman spectra revealed that a disordered face‐centered cubic phase was found in the composition range of x < 0.5, and an ordered primitive cubic spinel solid solution was achieved as x was beyond 0.5. Such a disorder–order transition near x = 0.5 was accompanied by the variation of composition‐induced cation occupancy. The Q × f value first kept increasing up to ~160 000 (GHz) in disordered ceramics, and then sharply decreased as an ordered structure appeared at x ≥ 0.5. An obvious decrease in τf value was also accompanied by the appearance of an ordered structure. The minimum τf value (~ ?20 ppm/°C) was obtained in the x = 0.75 sample with the highest structural order degree. These results demonstrated that microwave dielectric properties of current spinel ceramics could be successfully modified by adjusting their structural order degree, which could be appropriately adopted for the design of spinel‐structured materials with favorable properties. 相似文献
11.
《Ceramics International》2022,48(16):23044-23050
Nd[(Mg1-xZnx)1/2Ti1/2]O3 perovskite ceramics (x = 0, 0.2, 0.4, 0.6, 0.8) are prepared by the solid-state reaction method. The effects of Zn2+ substitution on the structure, microstructure, especially the B-site 1:1 cation ordering and microwave dielectric properties have been investigated. Sintered Nd[(Mg1-xZnx)1/2Ti1/2]O3 ceramics all adopt dense microstructure, along with increased dimensional uniformity as Zn2+ substitution. All the ceramics are confirmed to have B-site 1:1 ordered monoclinic perovskite structure with P21/n space group. Atomic mass difference of B-site elements might be an important factor affecting the B-site 1:1 cation ordering. HRSTEM observation suggest that the doped Zn2+ cations have roughly entered the Mg2+ sites to promote 1:1 cation ordering. The degree of the 1:1 cation ordering can be negatively reflected by the full width at half maximum (FWHM) of F2g(B) mode at 372 cm?1 in Raman spectra. With Zn2+ doping, the degree of the 1:1 cation ordering first increases then decreases, and reaches its maximum at x = 0.6. Meanwhile the best combination of microwave dielectric properties is obtained, as εr = 31.4, Q × f = 74,000 GHz, τf = ?44 ppm/°C. It is found that the long-range ordering not only decreases the dielectric loss but also affects the dielectric constant, providing a theoretical foundation to understand further the correlation between ionic configuration and microwave dielectric properties. 相似文献
12.
Xiaohua Zhang Yao Zhang Jie Zhang Bin Peng Zhenkun Xie Lixin Yuan Zhenxing Yue Longtu Li 《Journal of the American Ceramic Society》2014,97(10):3170-3176
Microwave dielectric properties and thermally stimulated depolarization currents (TSDC) of (1?x)Ba0.6Sr0.4La4Ti4O15–xTiO2 (x = 0, 0.01, 0.02, 0.05, and 0.1) ceramics were studied. X‐ray diffraction analysis indicates that the specimens show a hexagonal perovskite structure; however, with an increase of x to 0.1, TiO2?δ as a secondary phase can be detected in the ceramics. The variation of TiO2 content has a significant effect on the dielectric properties of (1?x)Ba0.6Sr0.4La4Ti4O15–xTiO2 at microwave frequency. The dielectric permittivity of ceramics increases from 44 to 49 with the increase of TiO2 content. The Qf value is in the range of 39 300–53 400 GHz. However, the temperature coefficient of resonant frequency (τf) changes from ?7.5 to–9.4 ppm/°C, and then turns to +3.9 ppm/°C. A near zero τf value can be obtained by tuning the content of TiO2 addition. TSDC was also employed to analysis the extrinsic loss mechanism. Utilizing a fixed polarization condition, the TSDC relaxation peaks are present, which are generated by oxygen vacancies. And the concentration of oxygen vacancies increases with the increase of TiO2 content. It can be concluded that the extrinsic dielectric loss is dominated by microstructure and oxygen vacancy defects. 相似文献
13.
Acceptor‐doped BaTiO3 powders of formula: BaTi1?xHoxO3?x/2?δ/2: x = 0.0001, 0.001, 0.01, 0.03, and 0.07, were prepared by sol‐gel synthesis, fired at 800°C–1500°C and either quenched or slow‐cooled to room temperature. Electrical properties of ceramics depended on firing conditions, Ho content, and cooling rate. Pellets of all x values fired at 800°C–1000°C were insulating and, from the presence of OH bands in the IR spectra, charge balance appeared to involve co‐doping of Ho3+ and H+ ions without necessity for oxygen vacancy creation. At higher firing temperatures, OH bands were absent. Pellets fired at 1400°C in air and slow cooled were insulating for both low x (0.0001) and high x (0.07) but at intermediate x (0.001 and 0.01) passed through a resistivity minimum of 20–30 Ω cm at room temperature, attributed to the presence of Ti3+ ions; it is suggested that, for these dilute Ho contents, each oxygen vacancy is charge compensated by one Ho3+ and one Ti3+ ion. At higher x, charge compensation is by Ho3+ ions and samples are insulating. A second, more general mechanism to generate Ti3+ ions, and a modest level of semiconductivity, involves reversible oxygen loss at high temperatures. 相似文献
14.
Structure Evolution and Enhanced Microwave Dielectric Characteristics of (Sr1−xCax)La2Al2O7 Ceramics
Lei Yi Lei Li Xiao Qiang Liu Xiang Ming Chen 《Journal of the American Ceramic Society》2014,97(11):3531-3536
(Sr1?xCax)La2Al2O7 (0.1 ≤ x ≤ 0.5) ceramics were prepared by a standard solid‐state reaction method. Their densification behavior and microwave dielectric properties were investigated together with the structural evolution. X‐ray diffraction analysis indicated that the major phase of Ruddlesden–Popper structure with n = 2 was obtained for all the compositions investigated here. Partial Ca substitution improved the sintering behavior of SrLa2Al2O7 ceramics. More importantly, microwave dielectric characteristics were enhanced in (Sr1?xCax)La2Al2O7 ceramics with compositions of x = 0.1~0.3. The stacking fault was confirmed by TEM observation in the present ceramics, and the microwave dielectric loss was influenced by it. The best combination of microwave dielectric characteristics was achieved for the composition of x = 0.1: εr = 19.9, Qf = 135 400 GHz and τf = ?18.5 ppm/°C. 相似文献
15.
The structure stabilities of double perovskite ceramics‐ (1 ? x) Ba(Mg1/2W1/2)O3 + xBa(Y2/3W1/3)O3 (0.01 ≤ x ≤ 0.4) have been studied by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and Raman spectrometry in this study. The microwave dielectric properties of the ceramics were studied with a network analyzer at the frequency of about 8–11 GHz. The results showed that all the compounds exhibited face‐centered cubic perovskite structure. Part of Y3+ and W6+ cations occupied 4a‐site and the remaining Y3+ and Mg2+ distributed over 4b‐site, respectively, and kept the B‐site ratio 1:1 ordered. Local ordering of Y3+/Mg2+ on 4b‐site and Y3+/W6+ cations on 4a‐site within the short‐range scale could be observed with increasing Y‐doping content. The decomposition of the double perovskite compound at high temperature was successfully suppressed by doping with Y on B‐site. However, Ba2Y0.667WO6 impurity phase appeared when x > 0.1. The optimized dielectric permittivity increased with the increase in Y doping. The optimized Q × f value was remarkably improved with small amount of Y doping (x ≤ 0.02) and reached a maximum value of about 160 000 GHz at x = 0.02 composition. Further increasing in Y doping led to the decrease in Q × f value. All compositions exhibited negative τf values. The absolute value of τf decreased with increasing Y‐doping content. Excellent combined microwave dielectric properties with εr = 20, Q × f = 160 000 GHz, and τf = ?21 ppm/°C could be obtained for x = 0.02 composition. 相似文献
16.
High permittivity (1−x)Bi1/2Na1/2TiO3‐xPbMg1/3Nb2/3O3 ceramics for high‐temperature‐stable capacitors
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Fanting Hu Xuefeng Chen Ping Peng Fei Cao Xianlin Dong Genshui Wang 《Journal of the American Ceramic Society》2018,101(10):4434-4440
(1?x)Bi1/2Na1/2TiO3‐xPbMg1/3Nb2/3O3[(1?x)BNT‐xPMN] ceramics have been fabricated via a conventional solid‐state method for compositions x ≤ 0.3. The microstructure, phase structure, ferroelectric, and dielectric properties of ceramics were systematically studied as high‐temperature capacitor materials. XRD pattern certified perovskite phase with no secondary phase in all compositions. As PMN concentration increased, the phase of (1?x)BNT‐xPMN ceramics transformed from ferroelectric to relaxor gradually at room temperature, with prominent enhancement of dielectric temperature stability. For the composition x = 0.2, the temperature coefficient of capacitance (TCC) was <15% in a wide temperature range from 56 to 350°C with high relative permittivity (>3300) and low dielectric loss (<0.02) at 150°C, which indicated promising future for (1?x)BNT‐xPMN system as high‐temperature stable capacitor materials. 相似文献
17.
《Ceramics International》2015,41(4):5872-5880
Effects of Zr-substitution on the structure, microstructure and microwave dielectric properties of Ba(Ni1/3Nb2/3)O3 ceramics have been investigated. A small amount of Zr-substitution facilitates the densification of Ba(Ni1/3Nb2/3)O3 ceramics. Within x≤0.05, the densification temperature decreases with increasing x in Ba[(Ni1/3Nb2/3)1−xZrx]O3, while it turns to increase for x>0.05. With increasing x, the grains become more homogeneous and closely contacted, and significantly increase in size for x=0.15–0.20. The B-site cations 1:2 ordering is destroyed by Zr-substitution, and only stabilizes for x≤0.04. B-site cations 1:1 ordering starts to form in x=0.04, and the 1:1 ordering degree first increases and then decreases with increasing x. Qf value decreases slightly in x=0.01 and then increases monotonously with x increasing from 0.02 to 0.20. The destroyed 1:2 ordering structure is responsible for the decreased Qf value in x=0.01, while the improved grain configuration dominates the increase of Qf value for x=0.02–0.20. The dielectric constant εr increases monotonously with increasing x, due to the higher polarizability of Zr ion than the average value of Ni/Nb ions. The temperature coefficient of resonant frequency τf shifts from negative to positive through zero with increasing x, which is ascribed to the highly positive τf value of the end member BaZrO3. The significant improvement of microwave dielectric properties has been achieved for x=0.10, higher εr, higher Qf as well as near zero τf value have been obtained: εr=31.8, Qf=36,100 GHz, τf=7.8 ppm/°C. 相似文献
18.
Study of the microwave dielectric properties of (La1−xSmx)NbO4 (x=0‐0.10) ceramics via bond valence and packing fraction
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Mi Xiao Qingqing Gu Ziqi Zhou Ping Zhang 《Journal of the American Ceramic Society》2017,100(9):3952-3960
The (La1?xSmx)NbO4 (x=0‐0.10) ceramics were prepared by the conventional solid‐state reaction method. The microstructure and the microwave dielectric properties were discussed in detail. The X‐ray diffraction patterns of (La1?xSmx)NbO4 (x=0‐0.10) showed that only a single monoclinic fergusonite structure of LaNbO4 could be found. The dielectric constant (εr) was affected by the dielectric polarizabilities and the B‐site bond valence. The variation trend of Q×f0 was in accordance with packing fraction. The temperature coefficient of resonant frequency (τf) had a close relationship with the B‐site bond valence, which was determined by the bond strength and bond length. When sintered at 1325°C for 4 hours, the (La1?xSmx)NbO4 ceramics with x=0.08 exhibited enhanced microwave dielectric properties: εr=19.37, Q×f0=62203 GHz and τf=2.57 ppm/°C. In addition, we made an overview about the ceramics that possess the same packing fraction and bond valence relationships, the results show that this structure‐property relationship has a wide applicability. 相似文献
19.
Microwave Dielectric Properties and Thermally Stimulated Depolarization Currents of (1 − x)MgTiO3–xCa0.8Sr0.2TiO3 Ceramics
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Jie Zhang Zhenxing Yue Yuanyuan Zhou Xiaohua Zhang Longtu Li 《Journal of the American Ceramic Society》2015,98(5):1548-1554
(1 ? x)MgTiO3–xCa0.8Sr0.2TiO3 (0.04 ≤ x ≤ 0.2, MT‐CST) composite ceramics were prepared by the conventional solid‐state reaction process. The phase composition, microwave dielectric properties, and microwave dielectric loss mechanisms were studied. Ca0.8Sr0.2TiO3 was employed as a τf compensator for MgTiO3, and they coexisted well without forming any secondary phases. Interestingly, significant dielectric relaxations associated with oxygen vacancy defects were observed in all the MT‐CST ceramics through the dielectric‐temperature spectra. Thermally simulated depolarization current was therefore conducted to obtain the defects associated with extrinsic dielectric loss mechanisms. The concentrations of both defect dipole and in‐grain oxygen vacancies increased with the increasing x, which could induce microwave dielectric loss consequently. It demonstrated that the behaviors of Q × f were basically influenced by phase composition and defects here. Temperature‐stable ceramics can be achieved at x = 0.06, where the microwave dielectric properties were εr = 21.19, Q × f = 110 900 GHz (f = 9.295 GHz), and τf = ?0.9 ppm/°C, respectively. 相似文献
20.
Yang Lv Ruzhong Zuo Ying Cheng Chen Zhang 《Journal of the American Ceramic Society》2013,96(12):3862-3867
The novel low‐temperature sinterable (1 ? x)Ba3(VO4)2–xLiMg0.9Zn0.1PO4 microwave dielectric ceramics were prepared by cofiring the mixtures of pure‐phase Ba3(VO4)2 and LiMg0.9Zn0.1PO4. The phase structure and grain morphology of the ceramics were evaluated using X‐ray diffraction, Raman spectra, and scanning electron microscopy. The results indicated that Ba3(VO4)2 and LiMg0.9Zn0.1PO4 phases can well coexist in the sintered body. Nevertheless, a small amount of LiZnPO4 and some vanadate phases with low melting points were observed, which not only can influence the microwave dielectric properties of the ceramic but also can obviously improve the densification behavior at a relatively low sintering temperature. The near‐zero temperature coefficients of the resonant frequency (τf) could be achieved by adjusting the relative content of the two phases owing to their opposite τf values and simultaneously a desirable quality factor Q × f value can be maintained. No chemical reaction between the matrix ceramic phase and Ag took place after sintering at 800°C for 4 h. The ceramics with 45 vol% LiMg0.9Zn0.1PO4 can be well sintered at only 800°C and exhibit excellent microwave dielectric properties of εr ~ 10, Q × f ~ 64 500 GHz, and τf ~ ?2.1 ppm/°C, thus showing a great potential as a low‐permittivity low‐temperature cofired microwave dielectric material. 相似文献