Co-reporter:Burhan Ullah, Wen Lei, Zheng-Yu Zou, Xiao-Hong Wang, Wen-Zhong Lu
Journal of Alloys and Compounds 2017 Volume 695() pp:648-655
Publication Date(Web):25 February 2017
DOI:10.1016/j.jallcom.2016.11.107
•Sr(1-1.5x)CexTiO3 (0.4 ≤ x ≤0.6) ceramics were prepared by conventional solid state method.•Sample with x = 0.4 have single phase, while an impurity phase appears above x ≥ 0.45.•Addition of CeO2 facilitates large grain size, formation of Ovac and ordering.•With addition of CeO2 the εr and τf decreases while the Q × f values increase linearly.•Sample with x = 0.6 display a high permittivity of εr = 61, Q × f = 22682 GHz and τf = +5 pmm/°C.Phase formation, chemical structure and microwave (MW) dielectric behavior of A-site Ce-doped SrTiO3 ceramics sintered in close aluminum pipe have been investigated. Samples with x = 0.4 appeared cubic by X-ray diffraction (XRD) but exhibited splitting and superstructure reflections in the range of 0.45 ≤ x ≤ 0.6. X-ray photoelectron spectroscopy (XPS) analysis revealed the sample possesses mixed-valent states of Ti3+/Ti4+ upon oxygen vacancy formation. As the x value increases, the Q × f value increases slightly from 7569 to 22,682 GHz, but the temperature coefficient of resonant frequency (τf) decreases markedly from +372 to +5 ppm/°C. A novel combination of microwave dielectric properties: εr = 61, Q × f = 22,682 GHz and τf = +5 pmm/°C were achieved for composition Sr0.1Ce0.6TiO3 at 1300 °C for 3 h.
Co-reporter:Burhan Ullah, Wen Lei, Xiao-Qiang Song, Xiao-Hong Wang, Wen-Zhong Lu
Journal of Alloys and Compounds 2017 Volume 728(Volume 728) pp:
Publication Date(Web):25 December 2017
DOI:10.1016/j.jallcom.2017.08.292
•Sr(1–3x/2)CexTiO3 ceramics were prepared by using a conventional solid state method.•Evidence of structure ordering and mixed-valence state of Ti3+/4+ ions upon Ovac formation.•Evidence of the polar TO2 and TO4 modes and formation of polar nanoregions (PNRs).•High-temperature relaxor behavior rather than normal ferroelectric anomalies.•Existence of hysteresis loop and remnant polarization of ∼0.04 μC/cm2.Crystal-defect chemistry, and temperature dependent dielectric characteristics was investigated in Ce-doped SrTiO3 (Sr(1−3/2x)CexTiO3, x = 0.45 − 0.55) ceramics. X-ray diffraction (XRD) and transmission electron microscopy (TEM) shows the evidence of structure ordering. The samples with x = 0.45 and x ≥ 0.5 display different phase structure evolution features with mixed- valence states of Ti3+/Ti4+ upon oxygen vacancy formation. The doping of Ce(x) facilitated large grain size with a dense microstructure. Activation of polar modes TO2 and TO4 indicated the evidence of polar nanoregions (PNRs). The system displays features of high-temperature frequency-dependent relaxor behavior rather than sharper frequency-independent normal ferroelectric anomalies. These relaxations were found to be bulk effect associated with singly (VO•) and doubly (VO••) charged oxygen vacancies.
Co-reporter:Burhan Ullah, Wen Lei, Xiao-Qiang Song, Xiao-Hong Wang, Wen-Zhong Lu
Journal of the European Ceramic Society 2017 Volume 37, Issue 9(Volume 37, Issue 9) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jeurceramsoc.2017.03.046
A perovskite solid solution (1−x)(Sr0.5Ce0.5)TiO3+δ−xNdAlO3, x = 0.1 to 0.4 was prepared by conventional solid state method. X-ray diffraction spectra revealed a single phase with tetragonal structure, indicating that doping of NdAlO3 significantly stabilized the perovskite-like structure. The addition of NdAlO3 facilitated the formation of large plate-like grains with porous microstructure. The dielectric constant (εr) decreased with increasing x because of the small ionic polarizability of NdAlO3. The Q × f value was strongly dependent on the microstructure of these ceramics. The temperature coefficient of resonant frequency (τf) gradually shifted to near zero with a rise of x, which resulted from the decrease in tolerance factor (t). The solid solution with x = 0.4 sintered at 1550 °C for 4 h showed a good combination of dielectric properties: εr = 72, Q × f = 12052 GHz and τf = +5 pmm/°C.
Co-reporter:Zheng-Yu Zou, Ze-Hao Chen, Xue-Kai Lan, Wen-Zhong Lu, ... Wen Lei
Journal of the European Ceramic Society 2017 Volume 37, Issue 9(Volume 37, Issue 9) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jeurceramsoc.2017.03.038
Ba2Zn(1+x)Si2O(7+x) ceramics were prepared using the conventional solid-state method at 1200 °C for 3 h in air. Apart from the previously reported Ba2Zn(1+x)Si2O(7+x) (x = 0) with a monoclinic structure (C 2/c), the end-member compositions at x = −1 and 1 exhibit single-phase β-BaSiO3 with an orthorhombic structure (P212121) and BaZnSiO4 with a hexagonal structure (P63), and possess a coexistence of weak ferroelectricity and low-permittivity microwave dielectric properties. A reduction in Zn2+ content mainly decreases the intensity of the εr anomaly peak at lower temperature and increases the εr (or frequency) stability against temperature. The Zn2+-rich BaZnSiO4 phase has a τf value of −181 ppm/°C, whereas the τf value of Zn2+-free BaSiO3 phase decreases to −35.4 ppm/°C. The Zn2+ deficiency in Ba2ZnSi2O7 composition could inhibit the presence of BaZnSiO4 phase and improve the τf value, whereas excessive Zn2+ cations prompt the formation of the BaZnSiO4 phase to deteriorate significantly the τf value.
Co-reporter:Burhan Ullah, Wen Lei, Xiao-Qiang Song, Xiao-Hong Wang, Wen-Zhong Lu
Ceramics International 2017 Volume 43, Issue 18(Volume 43, Issue 18) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.ceramint.2017.09.012
Phase composition, structure stability, cations valance state, and relaxor-like-dielectric behavior of Sr(1–3/2x)CexTiO3 (SCT, x = 0.3, 0.4) solid solution were investigated systematically. The Sr(1–3/2x)CexTiO3 samples appear to be single phase within the detection limits of the technique, whereas the solid solution exhibits the higher angle doublet and triplet peak splitting associated with (200) and (321). X-ray photoelectron spectroscopy (XPS) analysis showed that the Ce substitution induces change in the cations valance state upon oxygen vacancies formation. The system exhibits features of low-frequency dependent relaxor-like-dielectric behavior rather than sharp frequency-independent anomalies. Besides this, two kind of relaxations were detected in the temperature range ≥ 350 °C. According to the electric modulus and ac conductivity analysis, the relaxor-like-dielectric behavior results from the long-range conduction associated with ionized vacancies and mixed state of Ti3+/4+ and Ce3+/4+ cations.
Co-reporter:Xiaorong Zhang, Guifen Fan, Wenzhong Lu, Yihong Chen, Xuefeng Ruan
Journal of the European Ceramic Society 2016 Volume 36(Issue 11) pp:2767-2772
Publication Date(Web):September 2016
DOI:10.1016/j.jeurceramsoc.2016.04.029
Not only the optical properties, but the microwave dielectric properties of Yttrium aluminium garnet (Y3Al5O12, YAG) ceramics prepared by co-precipitation method combined with spark-plasma sintering (SPS) were investigated by means of adjusting the factors of LiF additive, Nd dopant, and SPS process parameters. Results showed that the in-line transmittance of YAG ceramic with LiF sintered at 1360 °C was 81.8% in the infrared range. With increased sintering temperature, the quality factor (Q × f) and dielectric constant (εr) values of the pure YAG ceramics increased to the maximum and then decreased. The optimal microwave dielectric properties (Q × f = 89,810 GHz, εr = 10.63 and τf = −51.4 ppm/°C) are achieved for transparent YAG ceramics sintered at 1360 °C. The Q × f values of Nd:YAG ceramics were lower than those of the pure YAG ceramics. The optimal microwave dielectric properties of 2 at.%Nd:YAG ceramic cylinder can be obtained with the Q × f of 64,026 GHz, εr of 10.2 and τf of −64.8 ppm/ °C.
Co-reporter:Xiaorong Zhang, Wenzhong Lu, Guifen Fan, Xiaohong Wang
Advanced Powder Technology 2016 Volume 27(Issue 1) pp:295-298
Publication Date(Web):January 2016
DOI:10.1016/j.apt.2015.11.004
Highlights
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A new organic fuel is firstly adopted to prepare Y2O3 powders by combustion method.
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The fabricated Y2O3 powders own nano-particle size and well-dispersity.
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Addition of organic fuel decreases particle size and improve dispersity of the Y2O3.
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Rise in temperature improves crystallinity but increases particle size of the Y2O3.
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The improved combustion method is simple, energy-saving, and high-efficiency.
Co-reporter:Xiaorong Zhang, Guifen Fan, Xiaohong Wang, Wen Lei, Liang Fei, Wenzhong Lu
Ceramics International 2016 42(7) pp: 7962-7967
Publication Date(Web):15 May 2016
DOI:10.1016/j.ceramint.2016.01.192
Y2O3 ceramics with good dielectric properties were prepared via co-precipitation reaction and subsequent sintering in a muffle furnace. The effects of Nd doping and sintering temperature on microwave dielectric properties were studied. With the increase in sintering temperature, the density, quality factor (Q×f), and dielectric constant (εr) values of pure Y2O3 ceramics increased to the maximum and then gradually decreased. The Y2O3 ceramics sintered at 1500 °C for 4 h showed optimal dielectric properties: εr=10.76, Q×f=82, 188 GHz, and τf=−54.4 ppm/°C. With the addition of Nd dopant, the Q×f values, εr, and τf of the Nd: Y2O3 ceramics apparently increased, but excessive amount degraded the quality factor. The Y2O3 ceramics with 2 at% Nd2O3 sintered at 1460 °C displayed good microwave dielectric properties: εr=10.4, Q×f=94, 149 GHz and τf=−46.2 ppm/°C.
Co-reporter:Wen Lei, Yong-Yi Yan, Xiao-Hong Wang, Wei Lu, Zhou-Bing Yang, Wen-Zhong Lu
Ceramics International 2015 Volume 41(Issue 1) pp:521-525
Publication Date(Web):January 2015
DOI:10.1016/j.ceramint.2014.08.100
The phase composition, microstructure, dielectric properties and breakdown strength of (Mg0.9Zn0.1)2(Ti1−xMnx)O4 ceramics synthesized using a conventional solid-state reaction were investigated. The substitution of Ti4+ by Mn2+ can form a single spinel phase and result in a homogenous microstructure, which improves breakdown strength and reduces dielectric loss. Impedance spectroscopy results show that grain and grain boundary exhibit similar impedance properties and that the Schottky barrier in the grain boundary cannot be observed. When the x value is equal to 0.01, (Mg0.9Zn0.1)2(Ti1−xMnx)O4 ceramics with a high breakdown strength of 102 kV/mm (at 0.2 mm) and a low dielectric loss of 5.3×10−5 (at 6 GHz) can be obtained, which are beneficial in the development of high voltage solid-state pulse-forming lines.
Co-reporter:G.F. Fan, M.B. Shi, W.Z. Lu, Y.Q. Wang, Fei Liang
Journal of the European Ceramic Society 2014 Volume 34(Issue 1) pp:23-28
Publication Date(Web):January 2014
DOI:10.1016/j.jeurceramsoc.2013.07.028
To assist the development of applications for multilayer piezoelectric devices, the low-temperature sintering piezoelectric ceramics of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 with Li2CO3 and Sm2O3 additives were fabricated by a conventional solid-state reaction, and their structural and piezoelectric properties were studied. With the addition of Li2CO3, the minimum sintering temperature of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 piezoelectric ceramics was reduced from 1125 °C to 950 °C through the formation of a liquid phase and its piezoelectric properties showed almost no degradation. When the sintering temperature was below 950 °C, however, the piezoelectric properties degraded obviously. The additional Sm2O3 resulted in a significant improvement in the piezoelectric properties of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 ceramic with added Li2CO3. When sintered at 900 °C, the optimized properties of the 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 piezoelectric ceramic with 0.3 wt% Li2CO3 and 0.3 wt% Sm2O3 were obtained as d33 = 483 pC/N, k31 = 0.376, Qm = 73, ɛr = 2524, tan δ = 0.0178.
Co-reporter:Ping Fu, Yong Xu, Haohao Shi, Baohua Zhang, Xuefeng Ruan, Wenzhong Lu
Optical Materials 2014 Volume 36(Issue 7) pp:1232-1237
Publication Date(Web):May 2014
DOI:10.1016/j.optmat.2014.02.035
•Transparent MgAl2O4 ceramics were fabricated by using spark plasma sintering.•The effects of annealing temperature were studied by PALS and XPS.•The critical annealing temperature is 900 °C for the optical properties.•The concentration of oxygen vacancies decreased after annealed.•A certain annealing temperature is corresponding to the best microwave dielectric properties.Transparent MgAl2O4 ceramics were fabricated by using spark plasma sintering (SPS). The effects of annealing temperature on the optical and microwave dielectric properties were investigated by positron annihilation technique and X-ray photoelectron spectroscopy (XPS). The results showed that the optimal annealing temperature for the optical property improvement was 900 °C and the in-line transmittance was improved to 74.9% at the wavelength of 550 nm. The further elevation of annealing temperature damaged the optical performance due to the combination of oxygen vacancies. The Q × f values of transparent MgAl2O4 ceramics were an overall increase from 800 °C to 1200 °C, but decreased at 1300 °C. It can be concluded that the annealing temperature plays an important role in the Q × f value, while a certain annealing temperature is corresponding to the best microwave dielectric property.
Co-reporter:Wen Lei, Ran Ang, Xiao-Chuan Wang, Wen-Zhong Lu
Materials Research Bulletin 2014 50() pp: 235-239
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.10.003
Co-reporter:Ping Fu, Wenzhong Lu, Wen Lei, Yong Xu, Xuehua Wang, Jiamin Wu
Ceramics International 2013 Volume 39(Issue 3) pp:2481-2487
Publication Date(Web):April 2013
DOI:10.1016/j.ceramint.2012.09.006
Abstract
The optical properties and microwave dielectric properties of transparent polycrystalline MgAl2O4 ceramics sintered by spark plasma sintering (SPS) through homemade nanosized MgAl2O4 powders at temperatures between 1250 °C and 1375 °C are discussed. The results indicate that, with increasing sintering temperatures, grain growth and densification occurred up to 1275 °C, and above 1350 °C, rapid grain and pore growth occurred. The in-line light transmission increases with the densification and decreases with the grain/pore growth, which can be as high as 70% at the wavelength of 550 nm and 82% at the wavelength of 2000 nm, respectively. As the sintering temperature increases, Q×f and dielectric constant εr values increase to maximum and then decrease respectively, while τf value is almost independent of the sintering temperatures and remains between −77 and −71 ppm/°C. The optimal microwave dielectric properties (εr=8.38, Q×f=54,000 GHz and τf=−74 ppm/°C) are achieved for transparent MgAl2O4 ceramics produced by spark plasma sintering at 1325 °C for 20 min.
Co-reporter:Jia-Min Wu, Wen-Zhong Lu, Xiao-Hong Wang, Ping Fu, Meng Ni, Jin-Long Yang, Cheng Wang, Qing-Chuan Zeng
Journal of the European Ceramic Society 2013 Volume 33(13–14) pp:2519-2527
Publication Date(Web):November 2013
DOI:10.1016/j.jeurceramsoc.2013.04.015
Based on aqueous gelcasting-assisted solid-state method (AGASSM), improved aqueous gelcasting-assisted solid-state method (IAGASSM) was proposed to prepare the 45 wt% Ba0.6Sr0.4TiO3–55 wt% MgO (BSTM) ceramic powders. It is found that the BSTM ceramic powders prepared by IAGASSM are the most uniform with the smallest particles (Dav = 0.83 μm) than those prepared by solid-state method (SSM) and AGASSM. The phase compositions of the BSTM ceramic powders and ceramics from the prepared ceramic powders are the same whatever ceramic powder preparation method is adopted. Compared with SSM and AGASSM, the BSTM green samples and ceramics from ceramic powders prepared by IAGASSM are the most uniform. Furthermore, it is found that adopting IAGASSM to prepare ceramic powders could not only improve the dielectric properties of the BSTM ceramics considerably, but also decrease their sintering temperature.
Co-reporter:Jun Liang;Wenzhong Lu;Wen Lei;Guifen Fan
Journal of Materials Science: Materials in Electronics 2013 Volume 24( Issue 10) pp:3625-3628
Publication Date(Web):2013 October
DOI:10.1007/s10854-013-1294-z
Low-temperature sintered Li2TiO3-based ceramics for low temperature co-fired ceramic resonators were synthesized by a solid state reaction method. Their microwave dielectric properties were further improved by CeO2 addition. When the amount of CeO2 increased, the relative permittivity (εr) of the samples increased a little and then decreased. The quality factor (Q × f) of the samples was improved obviously for a higher standard reduction potential of cerium than that of titanium. The temperature coefficient of resonant frequency (τf) of the samples decreased with the increase of CeO2 addition. CeO2 mainly existed as a secondary phase and it facilitated the sintering of the Li2TiO3-based ceramics. Typical microwave dielectric properties of εr = 22.97, Q × f = 34,881 GHz, and τf = 33.12 ppm/°C were obtained for Li2TiO3 + 2 wt% ZnO–B2O3 frit + 0.9 wt% CeO2 ceramics sintered at 920 °C for 4 h. The addition of oxidizers was proved a promising route to improve the microwave dielectric properties of titanate ceramics sintered at low temperatures.
Co-reporter:Man Li;Wenzhong Lu;Wen Lei;Xiaohong Wang
Journal of Materials Science: Materials in Electronics 2013 Volume 24( Issue 8) pp:2672-2677
Publication Date(Web):2013 August
DOI:10.1007/s10854-013-1154-x
The aqueous gelcasting-assisted solid-state method (AGAS) and traditional solid-state reaction method (TSSR) were used to prepare Ba[(Co0.7Zn0.3)1/3Nb2/3]O3 (BCZN)-based ceramics. The effects of different powder-preparation methods on the microstructures and dielectric properties of the BCZN-based ceramics were investigated. X-ray diffraction analysis showed completely the same phase compositions regardless of the preparation method adopted. The relative permittivity (εr) did not significantly vary between the two methods. However, BCZN with CeO2-added ceramics prepared by AGAS had higher and more uniform density (6.374 g/cm3) and high quality factor of resonant frequency (Q × f) value (75,843 GHz) than those prepared by TSSR because of the more uniform microstructures, as shown by scanning electron microscopy images. The temperature coefficients of resonant frequency (τf = 7.4 ppm/°C) of the ceramics prepared by AGAS were also closer to zero than those prepared by TSSR.
Co-reporter:Huakai Li, Wenzhong Lu, Wen Lei
Materials Letters 2012 Volume 71() pp:148-150
Publication Date(Web):15 March 2012
DOI:10.1016/j.matlet.2011.12.048
Li2ZnTi3O8 ceramics doped with ZnO–B2O3 frit were prepared by the conventional solid-state reaction. The effects of the ZnO–B2O3 frit on the sintering characteristic, phase composition, microstructure and microwave dielectric properties of Li2ZnTi3O8 ceramics were investigated. A single-phase Li2ZnTi3O8 is formed and no secondary phase is found in the XRD patterns. It is also found that ZnO–B2O3 frit can lower the sintering temperature of the ceramics by about 200 °C without seriously deteriorating the microwave dielectric properties. Typically, the ceramics doped with 0.25 wt.% ZnO–B2O3 frit sintered at 950 °C show good microwave dielectric properties of εr = 25.34, Q × f = 61,660 GHz, and τf = − 12.98 ppm/°C.Highlights► Li2ZnTi3O8 is a new kind of low sintering temperature material. ► ZnO-B2O3 frit can lower the sintering temperature of Li2ZnTi3O8 to about 950 °C. ► The microwave dielectric properties of the Li2ZnTi3O8 ceramics are not seriously deteriorated.
Co-reporter:Jia-Min Wu, Xiao-Hong Wang, Yue-Nong Fan, Xiao Shi, Wen-Zhong Lu
Materials Research Bulletin 2011 46(12) pp: 2217-2221
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.09.005
Co-reporter:Jia-Min Wu, Wen-Zhong Lu, Wen Lei, Xiao-Chuan Wang
Materials Research Bulletin 2011 46(9) pp: 1485-1489
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.04.026
Co-reporter:Jun Liang, Wen-Zhong Lu, Jia-Min Wu, Jian-Guo Guan
Materials Science and Engineering: B 2011 Volume 176(Issue 2) pp:99-102
Publication Date(Web):15 February 2011
DOI:10.1016/j.mseb.2010.09.009
Li2TiO3 ceramics were prepared at the sintering temperatures from 1050 to 1250 °C. The optimal microwave dielectric properties were ɛr = 23.29, Q × f = 15,525 GHz (5.9 GHz), and τf = 35.05 ppm/ °C for the sample sintered at 1200 °C. The microwave dielectric properties were improved obviously when the Li2TiO3 ceramics were sintered at low temperatures with small additions of H3BO3 (B2O3 in the form of H3BO3). Only monoclinic Li2TiO3 was found in the pure or H3BO3-doped Li2TiO3 ceramics. About 1.0 wt.% H3BO3 addition aided the sintering of Li2TiO3 ceramics effectively while excessive H3BO3 (≥2.5 wt.%) was not favorable. Typically the best microwave dielectric properties were ɛr = 23.28, Q × f = 37,110 GHz (6.3 GHz), and τf = 30.43 ppm/ °C for the 1.0 wt.% H3BO3-doped Li2TiO3 ceramic sintered at 920 for 3 h, which is promising for LTCC applications.
Co-reporter:Jing Zhang 张菁;Wenzhong Lu 吕文中;Guifen Fan
Journal of Wuhan University of Technology-Mater. Sci. Ed. 2010 Volume 25( Issue 3) pp:361-364
Publication Date(Web):2010 June
DOI:10.1007/s11595-010-0001-7
The microstructures and electrical properties of Bi0.5(Na1−x−yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied. These ceramics were prepared by conventional ceramic technique. XRD analysis reveals that the ceramics possess almost pure perovskite phase when y⩽0.2. The SEM results show that, with more amounts of Li+, the crystalline grain growing speed is accelerated, and the sintering temperature can effectively be decreased. The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li+ and high amount of K+ have comparatively large piezoelectricity. The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition (DPT) at Td and Tc, respectively. The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr (27.6 μC/cm2) and lower coercive field Ec (37.5 kV/cm).
Co-reporter:Wen Lei, Wen-Zhong Lu, Jian-Hua Zhu, Xiao-Hong Wang
Materials Letters 2007 Volume 61(19–20) pp:4066-4069
Publication Date(Web):August 2007
DOI:10.1016/j.matlet.2007.01.017
The microstructures, phase compositions and microwave dielectric properties of ZnAl2O4–TiO2 spinel-based composites have been investigated. It is found that ZnAl2O4 cannot form a solid solution with TiO2. As TiO2 content increases, the εr and τf values increase gradually, while the Q · f values degrade by degrees. Under the same amount of TiO2 content, the εr and Q · f values increase initially and then decrease slightly with increasing sintering temperature, while the τf values increase slowly. The optimal microwave dielectric properties are achieved in (1 − x)ZnAl2O4–xTiO2 (x = 0.21) sintered at 1500 °C for 3 h with εr value of 11.4, Q · f value of 71,810 GHz (at about 6.5 GHz), and τf value of − 0.5 ppm/°C.
Co-reporter:Thomas H. Maugh II
Science 1981 Vol 214(4521) pp:644
Publication Date(Web):06 Nov 1981
DOI:10.1126/science.214.4521.644-a
Co-reporter:Wei Gong, Burhan Ullah, Wen Lei, Gui-Fen Fan, Xiao-Hong Wang, Wen-Zhong Lu
Ceramics International (15 February 2017) Volume 43(Issue 3) pp:
Publication Date(Web):15 February 2017
DOI:10.1016/j.ceramint.2016.11.111
The phase formation, microstructure, chemical structure, and microwave (MW) dielectric properties of the composite ceramics (1-x)Mg(1.04–3/2y)CeyTiO3-xCaTiO3 (MCT-CT) have been investigated systematically. The CaTiO3 and MgTiO3 phases coexist well with the formation of secondary phase MgTi2O5 based on X-ray diffraction. Chemical structure analysis reveals the existence of oxygen vacancies (VO••) whose concentrations increase with x, which consequently induce microwave dielectric loss. It has demonstrated that the behaviors of Q×f are influenced strongly by the phase composition and vacancy defects. Although an increasing amount of CaTiO3 can improve the dielectric constant (εr) of the sample slightly, it renders a decrease in the Q×f value instead. The τf value is strongly correlated to the compositions and the existing phases that can be controlled. An excellent combination of the MW dielectric properties εr∼23, Q×f∼70, 800 GHz, and τf∼0 ppm/°C was obtained at x=0.08, sintered at an optimal temperature of 1300 °C/3 h.
