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In this work, a new Zn 1- x Ni x MoO 4 (ZNMO) (x = 0.03) ceramic with low-dielectric constant, low-loss, and low-sintering temperature for X-band two-dimensional (2D) beam splitting is developed by solid-state reaction method. This ceramic has excellent microwave dielectric properties of ε r = 8.5, Q × f = 28192 GHz, τ f = −60.2 ppm/°C. The effects of Ni2+ substitution on the microwave dielectric properties of the ZnMoO 4 ceramic are studied in detail through crystal structure analysis, Raman spectroscopy, and first-principles calculations. For the first time, an array antenna for X-band 2D electromagnetic beam splitting is designed by using this ceramic as a substrate. The effects of the dielectric constant and dielectric loss on the radiation efficiency of the array antenna are revealed. The normalized reflection amplitude and reflection phase of the unit cell exceed 0.97 and cover 360°, respectively. The function of 2D electromagnetic beam splitting is verified by the overall far-field pattern of the array antenna. This work has the opportunity to promote the development of LTCC and microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

The sintering behavior, microstructure, and microwave dielectric properties of Li2(Mg0.96Ni0.04)SiO4 ceramics with different amounts of LBS and LBSCA glass were studied. This experiment is based on the traditional solid-state reaction method. In this work, the microstructure of the composite ceramics with different kinds of glass was analyzed by SEM. Excellent microwave dielectric properties of the composite ceramics were obtained with sintering at 900°C: ε r = 5.49, Q × f = 18,448 GHz at 16 GHz, τ f = −15.3 ppm/°C with 4 wt.% LBS glass, ε r = 5.58, Q × f = 20,248 GHz at 16 GHz, τ f = −15.2 ppm/°C with 2 wt.% LBSCA glass. The addition of CaO and Al2O3 helped to improve the efficiency of sintering in the Li2(Mg0.96Ni0.04)SiO4 ceramic. [ABSTRACT FROM AUTHOR]

The sintering and microwave dielectric properties of a ceramic material based on the mixing of Mg3B2O6 and Zn3B2O6 have been widely studied using first‐principles calculations and experimental solid‐state reactions. Characterization methods include the Network Analyzer, X‐ray, Raman diffraction, scanning electron microscopy, energy‐dispersive spectroscopy, and differential‐thermal and thermo‐mechanical analyzer. The increasing amount of Mg2+ results in the appearance of Mg2B2O5 and ZnO, and the mutual substitution (Mg2+ and Zn2+) phenomenon has emerged in Zn3B2O6 and Mg2B2O5. The mechanisms have been explained with the help of DFT calculations. The bond parameters and electron distributions of the ZnO4 tetrahedron and MgO6 octahedron have been modified due to substitution. The sintering, substitution, and phase formation properties have been analyzed quantitatively through the energy parameters. The best dielectric properties were obtained for x = 0.20 sintered at 950°C, εr = 6.47, Q × f = 89 600 GHz (15.2 GHz), τf = −48.6 ppm/°C, relative density = 96.7%. The mixing of Zn3B2O6 and Mg3B2O6 ceramics is a feasible method to obtain a ceramic with low sintering temperature and excellent dielectric properties. [ABSTRACT FROM AUTHOR]

The influence of Mg2+-ion substitution on the sintering and microwave dielectric properties of Li 2 CaSiO 4 ceramic was investigated using the traditional solid-state reaction method and density functional theory. X-ray diffraction, scanning electron microscopy, Raman spectrometry, network analysis and simultaneous thermal analysis were used to characterise the macro properties. The replacement of Ca2+-ion with Mg2+-ion led to the transformation of dodecahedron into tetrahedron. In addition, the bond length and bond population related to the calcium site decreased. The atom vibration and microstructure characteristics were modified due to the lattice distortion. The densification temperature decreased from 1000 °C to 925 °C. The relative density increased from 70% to 80.5%. The dielectric properties were improved, that is, ε r = 5.63, tanδ = 0.0019 at 8 GHz as 4% (molar ratio) Ca2+-ions were replaced by Mg2+-ions. [ABSTRACT FROM AUTHOR]

The microstructure, sintering behavior, and microwave dielectric properties of LiZn1−xCoxPO4 (x = 0.00-0.10) ceramics were investigated. All these materials were synthesized by the traditional solid-state reaction method. Component and microstructure of the ceramics were verified by x-ray diffraction (XRD) patterns and scanning electron microscopy (SEM), respectively. The substitution of Co2+-ion to Zn2+-ion would improve the densification level of composite ceramics, and the microwave dielectric properties would be changed accordingly. An excellent microwave dielectric property of LiZn1−xCoxPO4 (x = 0.00-0.10) was achieved when x = 0.07 (ɛr = 5.43, Q × f = 35,446 GHz at 15 GHz, τf = − 77.4 ppm/°C). In order to achieve reliable thermal stability, Pb1.5Nb2O6.5 was used to adjust its τf value. The LiZn0.93Co0.07PO4 ceramics with 6 vol.% Pb1.5Nb2O6.5 sintered at 750°C for 4 h shows a near-zero τf value of − 4.4 ppm/°C, ɛr = 6.09, Q × f = 14,305 GHz (at 15 GHz), and there was no chemical reaction between Pb1.5Nb2O6.5 and LiZn0.93Co0.07PO4. The composite ceramics are promising materials for millimeter-wave device applications in the field of low temperature co-fired ceramics. [ABSTRACT FROM AUTHOR]

Abstract: Activation energy and diffusion kinetics are important factors for grain growth and densification. Here, Bi2O3 was introduced into Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics via a presintered process to lower the reaction activation energy and to achieve low temperature sintering. Interestingly, Bi3+ ions entered the lattice and substituted for Fe3+ in the B‐site (i.e., a pure LiZn spinel ferrite). Also, SEM image results show that Bi2O3‐substituted LiZn ferrite ceramics have low critical temperature for grain growth (920°C), which is very advantageous for LTCC technology. This indicates that Bi2O3 is an excellent dopant for ceramics. Furthermore, to promote normal grain growth of the ceramics at low temperatures, different volumes of V2O5 additive were added at the final sintering stage. Results indicate that an optimal volume of V2O5 additive promotes grain growth (with no abnormal grains) and enhances magnetic performances of the ceramics at low sintering temperature. Finally, adding the optimal volume of V2O5 additive resulted in a homogeneous and compact LiZnTiBi ferrite ceramic with larger grains (average size of ~8 μm), high 4πMs (~4100 gauss), and low ΔH (~190 Oe) obtained (at 900°C). Moreover, the doping method reported in this study also provides a reference for other low temperature sintered ceramics. [ABSTRACT FROM AUTHOR]

A method for solving the current challenges in manufacturing hetero-laminated material systems using Low Temperature Co-firing Ceramics (LTCC) technique is introduced in this paper. The system contains all three major materials that widely used in the LTCC industry, Zn 2 SiO 4 ceramic, NiCuZn ferrite and silver. Previous reported methods either involve additional buffer layers which would increase the device thickness, or apply mechanical pressure during the co-firing which is not compatible to the standard LTCC process. Our method provides a facile route to manufacture hetero-laminated material systems that demands no buffer layer and follows the standard LTCC process. In this paper, four glass-free hetero-laminated material systems using LTCC technology, i.e. NiCuZn/Zn 2 SiO 4 /NiCuZn/Zn 2 SiO 4 /NiCuZn (termed “LTCC-5”), NiCuZn/Zn 2 SiO 4 -Ag/NiCuZn (termed “LTCC-3-NZAN”), NiCuZn/Ag/NiCuZn (termed “LTCC-3-NAN”) and NiCuZn/Zn 2 SiO 4 /NiCuZn (termed “LTCC-3-NZN”), have be were designed, manufactured and characterized. The shrinkage rates of these material systems show well-matched temperature spectrum. The sintering properties and interfacial diffusions of the material systems were characterized using optical microscopy, electron microscopy and Energy Dispersive Spectrometer (EDS) element mapping. Optical microscopy shows that all the material systems have well-defined multi-layered structure with controllable and tunable layer thickness. Electron microscopy images prove no microstructural cracks or defects at any of the hetero material interfaces. EDS analysis further proves that the inter-diffusions of the magnetic elements (Fe and Ni) at the NiCuZn/Zn 2 SiO 4 interface is minimized. Such property is essential for achieving high performance devices for applications such as power inductors and DC/DC converters. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel ceramic with excellent microwave dielectric properties is developed. • The improvement of the dielectric properties of ceramics by W6+ is revealed. • An all-ceramic patch for 5G signal enhancement is designed using this ceramic. • The device compensates for the attenuation of 5G signals within the wall. • This work provides a new idea for LTCC device design. In modern wireless communication systems, the transmission of 5G signals is substantially attenuated by obstacles, resulting in indoor receivers not receiving signals at all. To overcome this thorny problem, a novel Zn 0.97 Co 0.03 Mo 0.92 W 0.08 O 4 ceramic material with excellent microwave dielectric properties (ε r = 8.432, Q × f = 64096 GHz, τ f = -41.9 ppm/°C) sintered at 850 °C is developed by the solid-state reaction method. For the first time, an all-ceramic array patch for 5G signal enhancement is designed and demonstrated using this ceramic. This all-ceramic-based device not only effectively avoids the problem of matching co-fire between metal electrodes and ceramics, but also compensates for the attenuation loss of 5G signals in the wall. The intensity of the 5G signal is greatly improved from 0.02 to 1.62 by the focusing effect of the device. This function is verified by the intensity and phase of the near-field electric field. This work provides a new idea for the design of all-ceramic-based LTCC devices and broadens the application of microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

Microwave imaging has the advantages of high accuracy, non-contact and damage-free, but this puts forward higher requirements on the materials of imaging devices. Here, a novel Zn 0.96 Cu 0.04 MoO 4 ceramic is reported using a solid-state reaction process. The substitution behavior and microwave dielectric properties of the ceramic are systematically investigated by the crystal structure, microscopic morphology, and Raman spectroscopy. It exhibits excellent microwave dielectric properties (ε r = 8.66, Q× f = 32024 GHz, and τ f = −58.1 ppm/◦C) sintered at 825 °C. A 40 × 40 microstructure array for static microwave imaging is designed and demonstrated based on this ceramic substrate. The maximum spin-selective reflection difference of the LCP and RCP waves at 9.6 GHz is 0.926. The image of a Chinese character presented has a recognizable resolution, both from intensity differences and three-dimensional (3D) electric field arrows. The pair of mutually chiral microstructures have an angular space of 6° for experimental manipulation. This work opens up the application of microwave dielectric ceramics in the imaging field. • The Zn 1- x Cu x MoO 4 (x = 0.04) ceramic (825 °C) can obtain excellent microwave dielectric properties (ε r = 8.66, Q× f = 32024 GHz, τ f = −58.1 ppm/◦C). • According to microstructural analysis and Raman spectroscopy, an appropriate amount of Cu2+ substitution can regulate the ε r and improve the Q× f and τ f values. • Based on this ceramic, a 40 × 40 microstructure array for static microwave imaging is designed and demonstrated. • The pair of mutually chiral microstructures have an angular space of 6° for experimental manipulation. • This work opens up the application of microwave dielectric ceramics in the imaging field. [ABSTRACT FROM AUTHOR]

A novel low-loss and low-sintering temperature Zn 3- x Co x (VO 4) 2 (ZCVO) (x = 0.25) ceramic for enhanced polarization converters is developed by solid-state reaction methodology. This ceramic has excellent microwave dielectric properties (ε r = 13.6, Q× f = 32173 GHz (@10.1 GHz), τ f = −74.5 ppm/℃) and good chemical compatibility with Ag. According to microstructural analysis, Raman spectroscopy, and first-principles calculations, it is revealed that an appropriate amount of Co2+ substitution can enhance the density, regulate the dielectric constant (ε r), and improve the Q× f and τ f values. Based on this ceramic, an enhanced polarization converter is designed. The maximum efficiency is as high as 90.38%. And the performance of this polarization converter can be regulated by the ε r and dielectric loss of ZCVO ceramics. The mechanism and function of the polarization converter are revealed according to the electric field strength, current direction, and far-field pattern. This work expands the application of microwave dielectric ceramics. • The Zn3-xCox(VO4)2 (x = 0.25) ceramic has excellent microwave dielectric properties (εr = 13.6, Q×f = 32173 GHz, τf = −74.5 ppm/℃). • An appropriate amount of Co2 + substitution can improve the microwave dielectric properties. • Based on this ceramic, an enhanced polarization converter between linear polarization and circular polarization is designed. • The performance of this polarization converter can be regulated by the εr and Q×f of ZCVO ceramics. • This work provides a new idea for LTCC device design and expands the application range of microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

The microstructure, sintering and microwave dielectric properties of (1−x)LiZnPO 4 +xLiMnPO 4 (x = 0.0–1.0) composite ceramics were discussed specifically through density functional theory calculation and solid-state reaction experiment. The (1−x)LiZnPO 4 +xLiMnPO 4 (x = 0.0–1.0) composite ceramics were characterised using network analyser, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and differential–thermal and thermo-mechanical analyser. The solid solution of Mn2+-ion-doped LiZnPO 4 ceramic and Zn2+-ion-doped LiMnPO 4 ceramic formed when the LiMnPO 4 ceramic was added into the LiZnPO 4 ceramic. The modification of the bond length, bond population and electron density could be observed in the ZnO 4 tetrahedron and MnO 8 octahedron. Moreover, the densification window of the LiZnPO 4 ceramic decreased slightly. Experimental results were specifically explicated by the calculation result. Peak dielectric properties were obtained when x = 0.3 sintered at 800 °C, ε r = 5.83, Q × f = 71,007 GHz, τ f = −82.84 ppm/°C and relative density = 97.33%. The addition of the LiMnPO 4 ceramic is an effective method for improving the sintering and microwave dielectric properties of the LiZnPO 4 ceramic. • In this study, the experiment based on solid-state reaction was conducted to investigate the influence of LiMnPO 4 ceramic on the sintering and dielectric properties of LiZnPO 4 ceramic, and the first principle calculation based on density functional theory was performed to explicate the crystal variation in details. • A detailed study of variation mechanism with the help of density functional theory for the composite ceramic has been done for the first time. • Based on the combination of the solid-state reaction experiment and the first principle calculation, the effect of LiMnPO 4 ceramic addition on the microstructure, sintering and microwave dielectric properties of LiZnPO 4 ceramic was discussed. • The solid solution of Mn2+-ion-doped LiZnPO 4 ceramic and Zn2+-ion-doped LiMnPO 4 ceramic formed when the LiMnPO 4 ceramic was added into the LiZnPO 4 ceramic, which has been verified by both the calculation and experiment: the modification of the bond length, bond population, electron density and energy. • The densification window of the LiZnPO 4 ceramic decreased without sintering aids. The dielectric properties and densification level has been improved due to the formation of solid solution, ε r = 5.83, Q × f = 71,007 GHz, τ f = −82.84 ppm/°C and relative density = 97.33%. [ABSTRACT FROM AUTHOR]

(1-x)Li 2 (Mg 0.96 Ni 0.04)SiO 4 +xLiZn 0.93 Co 0.07 PO 4 composite ceramics were synthesised through solid-state reaction, and their sintering kinetics, microstructure and microwave dielectric properties were investigated. The perfect disconnection model was applied to explain the variation in grain growth with different x values and sintering temperatures. X-ray diffraction, scanning electron microscopy, thermo-mechanical analysis and network analysis were used to determine the macro and micro properties of the composite ceramics. Results showed that LiZn 0.93 Co 0.07 PO 4 ceramic could promote grain growth and grain boundary modification, due to the different levels of shear stress and free energy density of the Si-rich and P-rich phases. The shrinkage onset point of the composite ceramics was adjusted to achieve full densification at 900 °C. The peak microwave dielectric properties are ε r = 5.78, Q × f = 48,168 GHz at 16 GHz and τ f = −44.7 ppm/°C when x = 0.5, sintering temperature is 900 °C and relative density is 96.1%. Therefore, mixing LiZn 0.93 Co 0.07 PO 4 (pre-sintered) and Li 2 (Mg 0.96 Ni 0.04)SiO 4 (pre-sintered) ceramics is a feasible synthesis method for microwave dielectric materials with excellent sintering and dielectric properties. • The perfect disconnection model was applied to explain the variation in grain growth. • The composite ceramic could be densified at 900 °C. • Both the sintering and microwave dielectric properties have been improved. [ABSTRACT FROM AUTHOR]

The first principle calculation was conducted to predict the effect of Co2+ ion substitution on the crystal structure, electron density, formation energy and vibration properties of Li 2 MgSiO 4 ceramic. All the samples were synthesised through the solid-state reaction method. Variations in sintering and dielectric properties were analysed through X-ray diffraction, scanning electron microscopy, network analysis, Raman spectrometry, thermomechanical analysis and simultaneous thermal analysis. Bond length, bond population and electron distribution in a MgO 4 tetrahedron were modified due to the substitution of Mg2+ ion by Co2+ ion. The densification temperature was lowered from 1250 °C to 1050 °C with the addition of 5% (molar ratio) Co2+ ions. The sintering window was put forward slightly, and the vibration property was changed. The densification level and microwave dielectric properties were improved accordingly at following conditions: ε r = 5.75, Q × f = 26,500 GHz at 16 GHz, τ f = −9.4 ppm/°C and relative density = 95.2%. The dielectric and sintering properties of Li 2 MgSiO 4 ceramic could be enhanced with the substitution of Mg2+ ion by Co2+ ion. Image 1 • The first principle calculation was performed to expect crystal variation. • The solid-state reaction experiment was done to verify the result of calculation. • Lattice distortion could improve the densification level and dielectric properties. • The sintering temperature has been lowered due to lattice distortion. [ABSTRACT FROM AUTHOR]

In the field of microwave dielectric ceramics for patch antennas, it has always been a thorny issue to simultaneously satisfy high dielectric constant, low sintering temperature and low dielectric loss. Here, a CCZN (x = 0.04) composite ceramic with excellent microwave dielectric properties was developed. It can be found that an appropriate amount of Co2+ substitution can enhance the compactness, increase the dielectric constant (ε r), reduce the dielectric loss (tan δ) and enhance the temperature coefficient (τ f). The composite ceramic with excellent dielectric properties (ε r = 22.6, Q × f = 37,624 GHz, τ f = −64.9 ppm/°C) shows good sintering compatibility with Ag. Based on this composite ceramic, a high-performance patch antenna was designed for Beidou satellite navigation system (BDS). It presents a small size of 30 × 30*3.8 mm3 and excellent radiation performance (return loss = −32.9 dB, VSWR = 1.047, impedance bandwidth = 60.6 MHz, radiation efficiency = 94.6% and realized gain = 7.704 dB). This work promotes the application of microwave dielectric ceramics in the field of patch antennas. [ABSTRACT FROM AUTHOR]

• Na+ substitution effectively lowered sintering temperature and contributed to the optimization of Q × f value. • The dielectric constant tended to decrease, which was more conducive to signal transmission. • The τ f value was closely related to the distortion of [MgO 6 octahedron. • Excellent dielectric properties were exhibited at x = 0.06 with ε r = 10.474, Q × f = 45,868 GHz, and τ f = −69 ppm/ºC. The Mg 1-x Na 2x WO 4 (0 ≤ x ≤ 0.14) microwave dielectric ceramics were prepared through traditional solid-state reaction and sintered at 875−925 °C for 4 h. Compared with pure MgWO 4 ceramic, the samples with substituting Na+ for Mg2+ could be sintered at a lower temperature, the quality factor values and the densification of microstructure were obviously improved. Raman spectroscopy proved that the relative permittivity was related to the multiple phases and molecular polarizability. In addition, the distortion of [MgO 6 octahedron also changed, resulting in resonance frequency temperature coefficient varied nonlinearly from x = 0 to 0.14. Considering the applications of low temperature co-fired ceramics technology, the Mg 1-x Na 2x WO 4 (x = 0.06) ceramic sintered at 875 °C had the best performance. Not only did it have excellent microwave dielectric properties of ε r = 10.474, Q × f = 45,868 GHz, and τ f = −69 ppm /ºC, but also presented great chemical compatibility with the commonly used Ag electrode. [ABSTRACT FROM AUTHOR]

Low temperature co-fired ceramics (LTCCs) technology plays an important role in modern wireless communication. Zn 3- x Co x B 2 O 6 (x = 0–0.25) low temperature fired ceramics were synthesized via traditional solid-state reaction method. Influences of Co2+ substitution on crystal phase composition, grain size, grain morphology, microwave dielectric properties, bond energy, and bond valence were investigated in detail. X-ray diffraction analysis indicated that the major phase of the ceramics was monoclinic Zn 3 (BO 3) 2. Solid solution was formed with Co2+ substituted for Zn2+ because no individual phase that contained Co was observed. An increase in the amount of Co2+ substitution changed average grain sizes, and regrowth of grains were observed with Co2+ substitution. Appropriate amount of Co2+ substitution improved densification. With changes in Co2+ substitution, bond energy of major phase and average bond valence of B–O were positively correlated to temperature coefficient of resonant frequency. The Zn 2.927 Co 0.075 B 2 O 6 ceramic sintered at 875 °C for 4 h exhibited excellent microwave properties with ε r = 6.79, Q × f = 140,402 GHz, and τ f = −87.42 ppm/°C. This ceramic is regarded as candidate for LTCC applications. [ABSTRACT FROM AUTHOR]

Herein, the improvement of the microwave dielectric properties and sintering characteristics of Zn 1−x Bi x V x W 1−x O 4 (x = 0–0.15)-based ceramics is reported. The results showed that an appropriate amount of doping could not only reduce the optimum sintering temperature from 1100° to 900°C, but also enhance the densification of the microstructures and increase the Q×f value from 5351 to 42525 GHz. Additionally, various structural parameters including the phase composition, crystal structure, vibrational and chemical bond characteristics that are correlated with the dielectric properties were systematically investigated. By considering the chemical bond characteristics, the first-principles calculations and the acquired Raman spectra, the interaction between W-O is stronger than Zn-O in the ZnWO 4 structure, while the interaction between V-O is stronger than Bi-O in BiVO 4. Interestingly, when the Zn 0.97 Bi 0.03 V 0.03 W 0.97 O 4 -based ceramics were sintered at 900 °C, improved microwave dielectric properties were acquired (ε r =18.32, Q×f =42525 GHz, τ f =−67.51 ppm/°C), which provides a promising candidate in low-temperature co-fired ceramics technology. [ABSTRACT FROM AUTHOR]

The converter is an important component of integrated circuits. A novel planar converter was designed with heterogeneous ferrites (different permeability). The permeability of the ferrite distributed in the middle part and both ends of the planar converter is 70 and 500, respectively. Compared with the traditional converter, the designed one has a smaller size (4 mm × 4 mm × 0.55 mm), higher working frequency (3 MHz) and higher efficiency (91%). Co 0.01 Ni 0.39 Zn 0.43 Cu 0.17 Fe 1.98 O 4 (F70, permeability of 70) and Co 0.01 Ni 0.26 Zn 0.56 Cu 0.17 Fe 1.98 O 4 (F500, permeability of 500) ferrites were synthesised in our laboratory to fabricate such a heterogeneous planar converter. Bi 2 O 3 was used to modify the sintering mechanical properties of F70 and F500 ferrites and realise matching co-firing of these two materials. Bi 2 O 3 can coexist with both ferrites. A heterogeneous model was built based on the F70 + 0.8 wt%Bi 2 O 3 and F500 + 0.4 wt%Bi 2 O 3 ferrites, and the variations in geometry and stress were researched through finite element simulation. Simulation results indicate that matching co-firing of these two ferrites was achieved. The designed planar converter with a heterogeneous layer was fabricated with the F70 + 0.8 wt%Bi 2 O 3 and F500 + 0.4 wt%Bi 2 O 3 ferrites through the low-temperature co-fired ceramic technology. No crack and curving were observed at the heterogeneous interface, and the performance of the fabricated planar converter was consistent with that of the designed one. The quantification and simulation of sintering mechanical properties are promising methods to realise the matching co-firing of heterogeneous layers, which could promote the development of passive integration. [ABSTRACT FROM AUTHOR]

Abstract: A series of Bi4Ti3O12/Ni0.25Cu0.2Zn0.55Fe2O4 ferroelectric–ferromagnetic composites were prepared by the usual ceramic technology and sintered at 900°C to adapt to the low temperature cofired ceramic (LTCC) technology. Among all samples, the relative density changes in the range of 94.9–96.4% and reaches the highest value in the composite with 30wt% Bi4Ti3O12 (BIT). When BIT content increases from 0 to 90wt%, the magnetic and dielectric properties show different change trends: the permeability (real part) at 1MHz reaches the maximum 170 in the composite with 10wt% BIT at first, and then gradually decreases from 170 to 1.4, while the saturation magnetization decrease from 2.85×105 A/m to 1.6×104 A/m; the dielectric loss tangent obtains a maximum value about 0.47 in the composite with 10wt% BIT at first, and then decreases sharply, while the permittivity (real part) at 1MHz increases from 8.8 to 100.3. The Maxwell Garnett mixing rule was used to predict the magnetic and dielectric properties of the composites with different assumptions. The calculated results basing on BIT matrix were more approximate to the measured in comparison to that basing on ferrite matrix. [Copyright &y& Elsevier]

Abstract: The aim of this work is to lower the sintered temperature of M-type barium ferrite (BaM) by BaCu(B2O5) (BCB) additives. The effects of BCB additives on the sintering behavior, structure and magnetic properties of BaM were also discussed. It was found that the sintered density, saturation magnetization and initial permeability of BaM are modified obviously as small amount of BCB (1–4wt%) is added. Especially, when BaM with 3wt% BCB was sintered at 900°C, the single-phase BaM was obtained and showed excellent properties with sintered density of 4.88g/cm3, saturation magnetization of 61.4emu/g and initial permeability of 3.15. In addition, the SEM result revealed that the sample can be co-fired well with the Ag electrode at 900°C. The reason for this was attributed to be the formation of the BCB liquid phase. It suggests that this M-type barium ferrite can be used as LTCC substrate for millimeter wave circulator, filter and other magnetic microwave devices. [Copyright &y& Elsevier]

A detailed study was performed using the density function theory to research the mechanism of the improvement of the sintering and dielectric properties of Ni2+ substituted Zn 3 B 2 O 6 ceramic. The mechanism involved bond properties, electron density and formation energy. The synthesis process is based on the solid-state reaction method and characterized via scanning electron microscopy, X-ray energy-dispersive spectroscopy, Raman spectrometry, network analysis, differential thermal analysis and thermo-mechanical analysis. The Zn1 site was the priority to be substituted by Ni2+, and the substitution happened in all the Zn tetrahedrons. The activation energy and densification window decreased slightly, and the sintering property was modified. The bond property and electron distribution around the tetrahedron with Ni2+ changed, and densification level and dielectric performance of the ZBO ceramic improved (ε r = 6.9, Q × f = 91,000 GHz at 15 GHz, τ f = −55.6 ppm/°C with high relative density (97.1%) at 900 °C). • The first principle calculation was performed to research the mechanism of the improvement of the sintering and dielectric properties of Zn 3 B 2 O 6 ceramic with Ni2+ substitution. The mechanism involved bond properties, electron density and formation energy. • The Zn1 site was the priority to be occupied by Ni2+, and the substitution happened in all the Zn tetrahedrons. The activation energy and densification window decreased slightly, and the sintering property was modified. The bond property and electron distribution of Zn tetrahedron changed. • Densification level and dielectric properties of the ZBO ceramic improved (ε r = 6.9, Q × f = 91,000 GHz at 15 GHz, τ f = −55.6 ppm/°C and relative density=97.1% at 900 °C). [ABSTRACT FROM AUTHOR]

In this study, (1- x) ZnTiNb 2 O 8 - x CuTiNb 2 O 8 -0.4 wt%LBSCA (0 ≤ x ≤ 0.4) microwave dielectric ceramics prepared by solid-state sintering were investigated to obtain low-temperature co-fired ceramic (LTCC) materials with near-zero resonant frequency temperature coefficient. X-ray diffraction (XRD) pattern and Rietveld refinement results reveal that with the increase in x value, main phase of ceramics is transformed from ZnTiNb 2 O 8 to ZnNb 2 O 6 and new phases (CuTiNb 2 O 8 and Ti 3 O 5) are formed at x ≥ 0.3. The microwave dielectric properties are affected with the appearance and increase in content of the secondary phase. Scanning electron microscope (SEM) images indicate that sample grains are relatively uniform and dense at x = 0.2. Raman shift obtained from Raman spectra explain changes in dielectric constant. Results reveal that the desirable dielectric properties were obtained by sintering at 875 °C with x = 0.375: ε r = 35.01, Q × f = 19449 GHz, and τ f = -0.3 ppm/°C, and the highest Q × f value (~38711 GHz) was obtained by sintering at 900 °C with x = 0.2 in the study. [ABSTRACT FROM AUTHOR]

Herein, glass-free microwave dielectric ceramics CaMg 0.9-x Li 0.2 Zn x Si 2 O 6 (x = 0–0.36) with excellent microwave dielectric properties were prepared via traditional solid-state reaction method. Phase composition and crystalline structure were identified using X-ray diffraction (XRD), which confirmed that the ceramics contained more than one phase. Rietveld refinement method was utilized to analyze XRD data and obtain structural information, such as lattice parameters. SEM photographs showed that Zn2+ substitution could effectively promote densification of the ceramics. Microwave dielectric properties were obviously influenced by the combination of multiple phases. Combined with Raman spectra, influences of Raman shift and FWHM of vibration peaks on microwave dielectric properties were determined. The CaMg 0.9-x Li 0.2 Zn x Si 2 O 6 ceramic exhibited high performance at x = 0.28 with: Q × f = 68,190 GHz, ε r = 7.51 and τ f = −68 ppm/°C, when sintered at 900 °C. The studied ceramics are promising candidates for LTCC application. [ABSTRACT FROM AUTHOR]

In this work, Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics (x = 0–0.4) added with 3 wt% Li 2 O–B 2 O 3 –Bi 2 O 3 –SiO 2 (LBBS) glass were synthesised using the solid-state reaction method. The effects of substituting Co2+ for Mg2+in Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics on crystal structure, microstructure, densification, crystallisation and microwave dielectric properties were investigated. X-ray diffraction patterns showed that monoclinic Li 2 MgSiO 4 , monoclinic Li 2 ZnSiO 4 and orthorhombic Li 2 CoSiO 4 formed finite solid solution in Li 2 Mg 0.6− x Co x Zn 0.4 SiO 4 ceramics. Clear grain boundaries were observed via scanning electron microscopy. The substitution of Co2+ for Mg2+ increased grain size, densification, crystallinity degree and dielectric constant; it also reduced the dielectric loss of the ceramics to a certain extent. The absolute values of τ f were positively related to the crystallinity degree. Li 2 Mg 0.55 Co 0.05 Zn 0.4 SiO 4 ceramic added with 3 wt% LBBS and sintered at 900 °C exhibited considerable microwave dielectric properties of ε r = 5.8, Q × f = 47,518 GHz and τ f = −74.8 ppm/°C. Therefore, the ceramic is considered a candidate low-temperature co-fired ceramic material for substrate and filter applications. [ABSTRACT FROM AUTHOR]

Theoretical calculation and experimental verification were performed to investigate the effect of Ni2+-ion substitution on the microstructure, sintering behavior, and microwave dielectric properties of LiZnPO 4 ceramic. The crystal structure, electron density, formation energy, and vibration mode of the doped system were discussed on the basis of density functional theory. Samples were synthesized using the traditional solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, network analysis, differentia-thermal and thermo-mechanical analyses, and Raman spectrometry. The substitution of Ni2+ ions to Zn2+ ions could modify the bond length, bond population, and electron distribution of ZnO 4 tetrahedron. The vibration, microstructure, and sintering properties changed accordingly. The densification level and microwave dielectric properties improved ( ε r =5.57, Q × f = 63,951 GHz at 15 GHz, τ f = -79.5 ppm/°C, relative density = 97.27%) when 4% (molar ratio) Zn2+ ions were replaced by Ni2+ ions sintered at 825 °C. The Ni2+-ion substitution could enhance the dielectric and sintering properties of LiZnPO 4 ceramic. [ABSTRACT FROM AUTHOR]

In this study, B 2 O 3 –Li 2 CO 3 –SiO 2 –ZnO (BLSZ) glass was fabricated and employed as a sintering aid for Li 0.43 Zn 0.27 Ti 0.13 Fe 2.17 O 4 ferrites. The introduction of BLSZ glass could allow the ferrites to be sintered at low temperatures (~920 °C) while maintaining a pure spinel phase. The results obtained from scanning electron microscopy revealed that BLSZ glass significantly promoted grain growth because of the liquid phase formed during sintering, which resulted in a homogeneous morphology with high densification. The saturation induction and saturation magnetization reached maximum values of 286.7 mT and 78.7 emu/g, respectively, with the addition of an appropriate amount (1.5 wt %) of BLSZ glass. This result can be attributed to the larger grains that were formed with the assistance of the BLSZ glass. Correspondingly, the coercivity and ferromagnetic resonance linewidth reached minimum values of 247.9 A/m and 236.6 Oe, respectively. The main reasons explaining this result are considered to be the homogeneous morphology and the low porosity of the samples. Therefore, it is believed that BLSZ glass can enable co-firing between LiZn ferrites and silver electrodes, which is crucial for the realization of low temperature co-fired ceramic (LTCC) technology. Image 1 [ABSTRACT FROM AUTHOR]

Low-temperature-fired NiCuZn ferrites with Al 2 O 3 (0–2 wt%) addition were prepared via the conventional solid-state reaction. The effects of different Al 2 O 3 doping contents on phase composition, microstructure and magnetic properties, especially DC-bias-superposition characteristic, were investigated. Results indicated that the addition of an appropriate amount of Al 2 O 3 content to NiCuZn ferrites could increase coercivity and the thickness of the nonmagnetic grain boundaries, thereby increasing the demagnetising field and subsequently reducing the decrease rate of the magnetic permeability under superposition magnetic fields. Simultaneously, permeability and saturation flux density monotonously decreased with the increase in Al 2 O 3 doping content. With the addition of 1.5 wt% Al 2 O 3 , the sample obtained relatively high permeability (∼70.7) and perfect DC-bias-superposition characteristic (H 70% –840 A/m). This ferrite material has favourable application prospects for recognising chip inductors that can carry large currents. • Al 2 O 3 addition was mainly deposited at the grain boundaries. • Al 2 O 3 led to the increase of Hc and DC-bias-superposition characteristic. • Al 2 O 3 led to the decrease of density and permeability. • 1.5 wt% Al 2 O 3 added ferrites achieved permeability of ∼70.7 and H 70% –840A/m. [ABSTRACT FROM AUTHOR]

In this study, the crystal structure and magnetic properties ( B s , ΔH , and 4π M s ) of Li 0.35 Zn 0.30 Mn 0.05 Ti 0.1 Fe 2.05 O 4 (LiZnMnTi) ferrites sintered at low temperature doped with MgO-Al 2 O 3 -B 2 O 3 -SiO 2 (MABS) glass were investigated. The results indicated that a spinel phases LiZn ferrite was obtained at low temperatures (from 880 °C to 920 °C), which is very advantageous for LTCC technology. Moreover, additive of MABS glass can promote grain growth, improve densification and enhance gyromagnetic properties. In addition, for the LiZnMnTi ferrites sintered at 920 °C, when amounts of MABS glass reached 0.5  wt %, saturation magnetization increased from 141 mT to 304 mT, coercivity decreased from 512 A/m to 189 A/m, and FMR line width ( ΔH ) reduced from 749 to 262 Oe at ∼9.5 GHz. These findings confirmed that MABS glass had positive effects on low temperature co-fired ferrites. [ABSTRACT FROM AUTHOR]

NiCuZn ferrites doped with different Bi 2 O 3 contents (0–1 wt%) were prepared through conventional ceramic technology. Phase composition, microstructure and magnetic properties, especially power loss characteristic of these samples were investigated. In doping range, Bi 2 O 3 did not introduce heterozygous phases. Initial permeability and saturation flux density (Bs) initially increased and then decreased as Bi 2 O 3 content increased. Maximum initial permeability and Bs were obtained with 0.25 wt% and 0.5 wt% Bi 2 O 3 , respectively. The variation in Bs with doping content was consistent with the variation in density. The variation in coercive force (Hc) was opposite to the variation in Bs. The sample doped with 0.25 wt% Bi 2 O 3 obtained the lowest power loss, regardless of different frequencies and induction conditions. Therefore, NiCuZn ferrite with 0.25 wt% Bi 2 O 3 was the best choice for applications in chip power magnetic devices or modules. [ABSTRACT FROM AUTHOR]

In this study, cobalt-ion substitution was applied to improve the microstructure and microwave dielectric properties of (Zn 0.7 Mg 0.3 ) 1-x Co x TiO 3 ceramics. (Zn 0.7 Mg 0.3 ) 1-x Co x TiO 3 ceramics were obtained via the conventional solid-state route, and Li 2 O:B 2 O 3 :SiO 2 :CaO:Al 2 O 3 (LBSCA) glass was used as a sintering aid to decrease the sintering temperature to 900 °C. X-ray diffraction analysis indicated that (Zn, Mg, Co)TiO 3 was the main crystalline phase. Scanning electron microscopy showed that proper cobalt-ion substitution promoted the densification and homogeneity of crystal grains in the (Zn 0.7 Mg 0.3 ) 1-x Co x TiO 3 system. At x = 0.075, the sample sintered at 900 °C with 1 wt% LBSCA glass formed a dense microstructure and exhibited excellent microwave dielectric properties of ε r  = 21.602, Q × f  = 80,040 GHz and τ f  = −70.24 ppm/°C. [ABSTRACT FROM AUTHOR]

Abstract: The Ni–Cu–Zn ferrites with different contents of Bi4Ti3O12 ceramics (1–8wt%) as sintering additives were prepared by the usual ceramic technology and sintered at 900°C to adapt to the low temperature co-fired ceramic (LTCC) technology. The magnetic and dielectric properties of the ferrite can be effectively improved with the effect of an appropriate amount of Bi4Ti3O12. For all samples, the ferrite sintered with 2wt% Bi4Ti3O12 has relatively high density (98.8%) and permeability, while the ferrite with 8wt% Bi4Ti3O12 has relatively good dielectric properties in a wide frequency range. The influences of Bi4Ti3O12 addition on microstructure, magnetic and dielectric properties of the ferrite have been discussed. [Copyright &y& Elsevier]

Abstract: Ferroelectric–ferromagnetic composites were prepared by the usual ceramic technology combined with the sol–gel method and sintered at 900°C to adapt to the low-temperature co-fired ceramic (LTCC) technology. The ferroelectric ceramics in reasonable amounts can effectively decrease the RF loss, dielectric loss and increase the saturation magnetization. Variations of permeability, dielectric constant and loss tangent with the frequency in the range of 1MHz–1.8GHz have been discussed. The microstructures of the sintered ceramics were analyzed by scanning electron microscope (SEM). The influences of different composition on the electromagnetic properties of the composites have been investigated. [Copyright &y& Elsevier]