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In the present work, Li 0.35 Zn 0.30 Mn 0.05 Ti 0.15 Fe 2.15 O 4 ferrites were successfully synthesized via solid-state reaction method with the assistance of Bi 2 O 3 -MgO mixture. It was observed that a pure spinel phase could be formed at low temperatures (880 °C–920 °C), suggesting the compatibility of co-firing with silver internal electrodes. The employment of Bi 2 O 3 -MgO mixture could not only achieve the low-temperature sintering, but also facilitate the grain growth and subsequently promote the magnetic properties. SEM results revealed that the ferrites grain size was significantly increased (from 1 to 20 μm) with an appropriate dopant addition (1.2 wt %). Meanwhile, the saturation induction was enhanced from 141.2 to 345.9 mT, the coercivity was decreased from 515.2 to 176.6 A/m, and the FMR linewidth was dramatically decreased from 749.0 to 245.0 Oe at 9.3 GHz. Thus it is expected that the improved properties will allow the Li 0.35 Zn 0.30 Mn 0.05 Ti 0.15 Fe 2.15 O 4 ferrites to be a promising candidate for low temperature co-fired ceramics (LTCC) applications. Image 1 • Low-temperature preparation of LiZn ferrites (below 950 °C). • All the samples with Bi 2 O 3 -MgO mixture show a typical spinel structure. • Bs increased from 141 to 345 mT with the ΔH decreased from 749 to 245 Oe. [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]

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]

The bound state in the continuum (BIC) and quasi-BIC are widely used in biosensing, lasers, and nonlinear optics due to their strong abilities of light-limiting and high-Q resonance. Most of the work is dedicated to achieving the goal of static conversion between BIC and quasi-BIC, but lacks sufficient attention to their dynamic continuous manipulation. To alleviate this situation, a type of graphene-metal hybrid metasurfaces for BIC and quasi-BIC of terahertz linearly polarized waves are proposed by combining the tunable properties of graphene with the C 2 asymmetry of the structure. The free continuous modulation can be achieved by the Fermi level driven by an external voltage. The transmission amplitude corresponding to the maximum radiation leakage is 0.13. The quasi-BIC can be actively modulated in the modulation range of 0.13–0.63, and the modulation depth is as high as 0.5. Based on this, the terahertz dynamic near-field imaging of five "UESTC" images with different contrasts is designed and simulated. All the features of the electric field intensity and arrow direction show good imaging results. This work provides a new way for the design of terahertz modulators based on metasurfaces, and enriches the applications of BIC and quasi-BIC. • A type of graphene-metal hybrid metamaterials for BIC and quasi-BIC of terahertz waves are proposed. • The free continuous modulation can be achieved by the Fermi level driven by an external voltage. • The terahertz dynamic near-field imaging of five "UESTC" images with different contrasts is developed. • This method provides a new idea for the design of terahertz modulators. [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]

• Low absolute TCR values could be achieved in the range of x = 0.4–0.8 and zero TCR could be realized around 0.6

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]

The comprehensive properties and sintering temperature of microwave dielectric ceramics are the key factors limiting their practical application. In this work, a novel strategy of complex (Co 1/3 Nb 2/3)4+ ions substituted and adding glass (Li 2 O-B 2 O 3 - SiO 2 -CaO-Al 2 O 3 : LBSCA) was proposed to greatly enhance the microwave dielectric properties of Ba 3 Ti 4- x (Co 1/3 Nb 2/3) x Nb 4 O 21 (0 ≤ x ≤ 12 mol%, x CN-BTN) ceramics. A new ceramic of (Co 1/3 Nb 2/3)4+ substitution improved hexagonal phase BTN was successfully fabricated and systematically investigated. As the increased of (Co 1/3 Nb 2/3)4+ ions concentration, the Q× f was greatly increased because of higher packing fraction, and the reduction in the [Nb1/Ti1O 6 ] octahedral distortion caused great changes of τ f. Besides, the P-V-L theory revealed that the Ti/Nb ratio greatly contributed in permittivity ε r , and the Nb-O bonds mainly affected dielectric loss, especially in Nb(1)-O2(1) bond. As a result, the superior microwave dielectric properties were obtained in 6CN-BTN ceramic sintered at 950 °C: ε r ∼40.99 ± 0.48, Q× f ∼17,310 ± 565 GHz, and τ f ∼8.62 ± 4.34 ppm/°C. More encouragingly, 6CN-BTN showed good compatibility with silver, making it a promising K 40 LTCC material for filter and dielectric resonators. This study presented a new strategy to improve the properties of BTN-based materials by complex ions substitution, which was expected to provide a general approach for the design of advanced microwave dielectric ceramics for other material systems. • A novel strategy of (Co 1/3 Nb 2/3)4+ substituted was proposed to greatly enhance the microwave performance of BTN ceramics. • (Co 1/3 Nb 2/3)4+ ions can greatly change the [Nb/TiO 6 ] octahedral distortion, thus greatly improving the Q× f and τ f. • 6CN-BTN ceramic with high performance, low sintering temperature and temperature stable. • 6CN-BTN ceramics is expected to be a candidate material for K 40-LTCC ceramics. [ABSTRACT FROM AUTHOR]

In this study, a series of high-entropy [(Mg 1/2 Zn 1/2) 0.4+ x (Ni 1/3 Co 1/3 Mn 1/3) 0.6- x ] 2 TiO 4 (expressed as MZNCMT) (0.0 ≤ x ≤ 0.6) ceramics were prepared via the solid-state reaction, the high-entropy ceramics exhibited inverse spinel structure. The phase compositions, microstructures, and microwave dielectric properties were investigated. The results of x-ray diffraction (XRD) showed that a principal phase of [(Mg 1/2 Zn 1/2) 0.4+ x (Ni 1/3 Co 1/3 Mn 1/3) 0.6- x ] 2 TiO 4 ceramics, whereas the second phase of (Mg, Zn, Ni, Co, Mn)TiO 3 appeared when x ≤ 0.4. With the increase of x value, the relative density of the sample decreased, the unit cell volume first decreased and then kept expanding. This phenomenon could be attributed to the reduction of (Ni 1/3 Co 1/3 Mn 1/3)2 +. Good microwave dielectric properties were achieved: x = 0.0 (ε r = 17.17, Qf = 16500 GHz, τ f = −33 ppm/℃), x = 0.5 (ε r = 16.30, Qf = 53900 GHz, τ f = −30 ppm/℃) and x = 0.6 (ε r = 16.26, Qf =110800 GHz, τ f = −39 ppm/℃). The ε r value of MZNCMT ceramics is consistent with the theoretical dielectric constant (ε theo), indicating that ε r is mainly based on ion polarization. The Qf value were highly related to the packing fraction. Furthermore, the τ f value depended on the bond strength of A-site. [Display omitted] • The sintering property of Mg 2 TiO 4 was improved. • The τ f value has been improved about 50 %, going from −63 ppm/℃ to −30 ppm/℃. • This method of improving properties can be applied to other materials. • This ceramic has potential application prospects in mobile communication. [ABSTRACT FROM AUTHOR]

The effect of CaTiO 3 addition on the sintering behavior, microstructure, and magnetic and dielectric properties of NiCuZn/CaTiO 3 composite dual-performance materials was investigated. The crystal and microstructure were characterized by X-ray diffraction and scanning electron microscopy. The magnetic and dielectric properties were obtained by vibrating sample magnetometry and impedance analysis. The CaTiO 3 ceramic could coexist with the NiCuZn ferrite. The atom substitution occurred in the composite materials, and the increment in CaTiO 3 content led to a gradual decline in grain size of NiCuZn ferrite. The saturation magnetization and permeability decreased gradually as CaTiO 3 content increased, while the coercivity increased gradually. Meanwhile, the cut-off frequency and dielectric constant of the composite materials incremented, and all samples presented optimized performance with the increased sintering temperature. The NiCuZn/CaTiO 3 composite duel-performance materials exhibited excellent dielectric and magnetic properties. All in all, the addition of CaTiO 3 weakened the magnetic properties of the dual-performance material, while its dielectric properties were enhanced. These results would be useful for further study on NiCuZn/CaTiO 3 composite dual-performance materials. ● The NiCuZn and CaTiO 3 coexist, the saturation magnetization and permeability decreased, and the coercivity increased. ● The cut-off frequency and dielectric constant increased with the addition of CaTiO 3. ● The increased sintering temperature led to enhanced permeability, and the Q value also increased. [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]

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]

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]

Abstract High-performance dielectric materials for microwave communication requires low dielectric constants (ε r < 10), high quality factor (Qf) and near-zero temperature coefficient of resonance frequency (τ f). However, CaMgSi 2 O 6 ceramics typically exhibit low Qf and largely negative τ f , despite its low ε r. In this study, nominal composition CaMg 1- x Cu x Si 2 O 6 (0 ≤ x ≤ 0.16) ceramics were synthesized via a solid-state reaction. Enhanced microwave dielectric properties were achieved in the x = 0.04 ceramic sintered at 1250 °C with ε r = 7.41, Qf = 160 100 GHz (two times better than the previously reported values), and τ f = −42 ppm/°C. Benefited from the optimal CuO doping, this enhancement in microwave dielectric property was realized by the contribution of order structure and the densification. Excess CuO doping, which can lead to a phase transition (from C 2/ c to P 2 1 / c), could degenerate the microwave dielectric properties of the CaMgSi 2 O 6 ceramics. Considering the excellent microwave dielectric properties, the CuO-doped CaMgSi 2 O 6 ceramic is a promising candidate material for microwave communication applications. Graphical abstract Image 1 Highlights • Enhanced dielectric properties of CaMgSi 2 O 6 were realized by moderate CuO doping. • The maximum Qf of CuO-doped CaMgSi 2 O 6 is ∼two times higher than previously reported. • Mg defect can lead to phase transition of CaMgSi 2 O 6 from C 2/ c to P 2 1 / c. • Excess CuO doping could degenerate the microwave dielectric properties. [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]

Multiferroic Bi 1−x Sm x FeO 3 (x = 0.00–0.05) ceramics were prepared by a conventional solid-state reaction method, and effects of Sm 3+ ions on crystal structure, magnetic and dielectric properties were investigated. TGA-DSC studied the synthesis process of pure BiFeO 3 sample and confirmed the synthesis temperature was about 825 °C. For all samples, they were rhombohedral distorted perovskite structure of R-3c space group. Lattice constants and particle sizes decreased based on the data of XRD and Rietveld refinement. Morphologies of the samples were determined with Scanning Electron Microscopy proving the grain to be shrinkage. With increasing of Sm 3+ ions, saturation magnetization of Bi 0.97 Sm 0.03 FeO 3 material at 5000 Oe was about 1.5 times larger than that of pure BiFeO 3 , while the coercivity increased from 87.3 Oe to 121.3 Oe. In a wide range frequency from 1 MHz to 1.6 GHz, dielectric constant kept a stable value. With Sm 3+ increasing, dielectric constant increased from 27 to 46, while dielectric loss kept a low value. [ABSTRACT FROM AUTHOR]

LiZnMnTi ferrite, composed of Li 0.35 Zn 0.3 Mn 0.05 Ti 0.1 Fe 2.07 O 4, possesses superior magnetic properties when sintered at high temperature. To obtain great performance at low sintering temperature (below the melting point of Ag), Li 2 CO 3 B 2 O 3 Bi 2 O 3 SiO 2 (LBBS) glasses was introduced into the LiZnMnTi ferrites. Results show that the LBBS glass makes great contributions to achieve low temperature sintering (∼920 °C) and the ferrites keep superior magnetic properties. On the one hand, the additive of LBBS glass (0.50 wt%) can largely improve saturation induction (∼330 mT), remanence square ratio (∼0.83) and lower coercive force (∼180 A/m). Meanwhile, a low ferromagnetic resonance line width (∼240 Oe) at 9.3 GHz was obtained. A higher saturation magnetization (∼56 emu/g) was also attained when amount of the glass additive is around 0.50 wt%. The results indicate that the LBBS glass is a good sintering aid for lowering the firing temperature of LiZnMnTi ferrites for microwave device applications. [ABSTRACT FROM AUTHOR]

A series of the Ba 1.5 Sr 1.5 Co 2- x Mn x Fe 23 O 41 (x = 0.0–0.5) hexaferrites was prepared by the conventional solid-state reaction method. The crystalline phase structure, microstructure and magneto-dielectric properties of samples were investigated. Z-type and W-type phases were detected in hexaferrites sintered at 1200 °C. Mn substitution can reduce the content of the second phase, changes the ion occupancy, magnetic moment, and electron hopping in hexaferrite. Therefore, the magnetic, DC resistivity, and dielectric properties were altered, and the losses were successfully reduced in the substituted samples. Particularly, the Ba 1.5 Sr 1.5 Co 1.8 Mn 0.2 Fe 23 O 41 hexaferrite has a more homogeneous crystal phase; its μ i is 18.5, f r exceeds 1 GHz, and the Snoek's constant reaches 18.55 GHz. At the same time, this hexaferrite were characterized by a relatively large magnetic quality factor and low dielectric losses (tan δ ε <0.05 below 500 MHz). This Z-type hexaferrite has excellent high-frequency magneto-dielectric properties and holds a potential for use in miniature antennas. • The results show that appropriate Mn substitution can increase the permeability, permittivity and Snoek's constant, and lower the magnetic and dielectric losses of Co 2 Z hexaferrites. • Favorable magneto-dielectric properties were obtained in the Ba 1.5 Sr 1.5 Co 1.8 Mn 0.2 Fe 23 O 41 hexaferrite. Its μ i is 18.5, Snoek's constant reaches 18.55 GHz, ε' around 16, and losses are low. • This ferrite can meet the requirements of miniaturized antennas. [ABSTRACT FROM AUTHOR]

At present, 5 G communication is developing rapidly, devices are becoming miniaturized, which requires the continuous emergence of materials with high dielectric constant. In this work, choosing Co2+ to substitute Li 1–2 x Co x Nb 0.6 Ti 0.5 O 3 (LCNT, 0 ≤ x ≤ 0.1) + 0.4 wt % LBSCA ceramics successfully achieved high permittivity ε r and temperature stable resonant temperature frequency coefficient τ f sintered at 950 ℃, including ε r ∼62, Q× f ∼6255 GHz, and τ f ∼0.97 ppm/℃ (x = 0.02), ε r ∼56.55, Q× f ∼7090 GHz, and τ f ∼− 28.07 ppm/℃ (x = 0.06). Meanwhile, the influence of Co2+ on LNT ceramics for phase composition, micro-structure, microwave dielectric performance and Raman vibration had been studied in detail. All samples belonged to M phase. Rod-like or blocky grains were gradually refined, indicating that Co2+ had the effect of grain refinement. In microwave dielectric performance, ionic polarizability played a leading role in ε r , Q× f value was positively correlated with the bulk density, τ f directly depended on the average repeatable layer N. In Raman spectroscopy, three modes of Raman vibration had been identified as translation or rotation of Li+ ions, Nb/Ti bond vibration, [Nb/TiO 6 ] octahedral vibration. To meet low temperature co-fired applications, the LCNT (x = 0.02) ceramic didn't react with Ag, which suggested it was achieving candidates for the next generation of medium K LTCC materials. • Adapting Co2+ ions control engineering + adding 0.4w t % LBSCA to realizing LTCC technology within the LCNT ceramics. • LC 0.06 NT ceramic maintained a high K and quality factor: ε r ~56.55, Q× f ~7090 GHz, τ f ~-28.07 ppm/℃ sintering at 950℃. • The enhanced microwave properties were attributed to the higher bulk density, and average repeatable layers N. [ABSTRACT FROM AUTHOR]

In this work, a new low loss Ba 3 Ti 4- x (Mn 1/3 Nb 2/3) x Nb 4 O 21 (MN-BTN, 0 ≤ x ≤ 12 mol%) ceramics configuration was presented through preparing by the solid-state route. The XRD patterns, Rietveld refinement, microstructure, and microwave properties were systematically analyzed. All the fabricated MN-BTN ceramics belonged to the hexagonal structure with a P 6 3 / mcm space group. More specifically, the 6MN-BTN ceramic exhibited a high relative density of ~92.3 %, homogeneous grains distribution with an average size of ~71.95 µm, and several excellent microwave dielectric properties: ε r = 59.67, Q× f = 16,226 GHz, τ f = +103.9 ppm/℃ sintered at 1220 ℃. The incorporation of 1.5 wt % BaCu(B 2 O 5) (BCB) compound within the 6MN-BTN ceramic not only effectively reduced the sintering temperature from 1220 ℃ to 950 ℃, but also the excellent microwave dielectric properties were maintained: ε r = 42.33, Q× f = 11,300 GHz, τ f = +24.7 ppm/℃. Interestingly, the 6MN-BTN + 1.5 wt % BCB ceramic showed better chemical compatibility with Ag. The proposed 6MN-BTN + 1.5 wt % BCB ceramic configuration could be regarded as a promising material for LTCC applications. • Adapting composite (Mn 1/3 Nb 2/3)4+ ions and adding BCB compound to realize low temperature co-firing BTN ceramics. • 6MN-BTN ceramic had excellent microwave dielectric properties: εr=59.67, Q×f=16226 GHz, τf=+103.9 ppm/℃ sintered at 1220℃. • Enhanced microwave properties were related to bulk density, uniform grain size, packing fraction, octahedral distortion. • BCB compound was an effective sintering aid, not only matched with Ag co-firing, but also validly improved τf. [ABSTRACT FROM AUTHOR]

● CaMg 1- x Na 2 x Si 2 O 6 microwave ceramics were fabricated via solid-state methods. ● The sintering temperature CaMg 0.97 Na 0.06 Si 2 O 6 was lower than that of CaMgSi 2 O 6. ● The P-V-L bond theory was utilized to explore the chemical bond characteristics and structure-performance relationships. ● The excellent microwave dielectric properties for CaMg 0.97 Na 0.06 Si 2 O 6 ceramics were: ε r = 7.573, Q × f = 35049 GHz, tan δ = 4.015 × 10−4 and τ f = −68.71 ppm/°C, when sintered at 1150 °C. The Na-doped diopside (CaMg 1- x Na 2 x Si 2 O 6 , x = 0–0.18) microwave dielectric ceramics were fabricated via solid-state reaction method. Three phases were identified through the XRD data that was refined with the Rietveld method to obtain structural information. The role of Na+ substitution to promote the densification process could be corroborated by the SEM images and relative density. The P-V-L bond theory was used to explore the chemical bond characteristics and structure-performance relationships. Through discussion, the dielectric constant was determined by relative density rather than the bond ionicity. The Q × f value was dominated by the lattice energy, lattice vibration and was also related to the relative density and grain size. And the linear thermal expansion coefficient was closely correlated with the τ f value. Excellent microwave dielectric properties, (ε r = 7.573, Q × f = 35049 GHz, tan δ = 4.015 × 10−4, τ f = −68.71 ppm/°C) and (ε r = 7.646, Q × f = 37844 GHz, tan δ = 3.706 × 10−4, τ f = −54.2 ppm/°C) were achieved for the CaMg 0.97 Na 0.06 Si 2 O 6 ceramics sintered at 1150 °C/3 h and 1200 °C/3 h, respectively. [ABSTRACT FROM AUTHOR]

• The electronic structure, chemical bond characteristics and microwave dielectric properties of Zn 1-x Co x WO 4 (x = 0–0.1) ceramics were investigated by First-principle calculations, Raman spectroscopy, XRD refinement and P-V-L theory. • Excellent dielectric properties were exhibited at x=0.02 with ε r = 15.03, Q×f = 59805GHz, τ f = −60.3ppm/°C. The electronic structure, chemical bond characteristics and microwave dielectric properties of Zn 1−x Co x WO 4 (x = 0–0.1) ceramics prepared by solid-state reaction were investigated by First-principle calculations, Raman spectroscopy, XRD refinement and P-V-L theory. According to the P-V-L theory and electronic structure calculations, the bond energy and covalency of W-O were stronger than that of Zn-O, which played a crucial role in the properties. The Raman spectra illustrated that appropriate Co2+ substitution was beneficial to the ordered structure. Additionally, the relative permittivity of the sample was mainly affected by the porosity and ionic polarizability, and the quality factor is determined by the microstructure, bond energy and packing fraction, and the τ f value is correlated with bond valence of W-O. This study showed how the Co2+ substitution not only reduces the dielectric loss and the signal delay time, but also improves the temperature stability. The composition (x = 0.02) exhibited remarkable properties: ε r = 14.22, Q×f = 59,805 GHz, τ f = −60.3 ppm/°C, providing a promising candidate for 5 G electronic equipment. [ABSTRACT FROM AUTHOR]

Designing of materials which can resist aging and corrosion in harsh reaction conditions is required to mitigate the omnipresent issue of electromagnetic interference pollution. Particularly, FeSiAl alloy is a relevant composite material, however, it always suffers aging and corrosion when exposed to crude saline environment. Herein, Carbon-encapsulated FeSiAl (FeSiAl@C) hybrid flakes are developed by catalytic chemical vapor deposition (CCVD) technique through the reaction of FeSiAl precursor with acetylene (C 2 H 2) gas at 300 °C for 5 min. The carbon coating efficiently improves the impedance matching characteristics of FeSiAl powder leading to enhance microwave absorption. Not only that, the carbon capsule also plays an effective shielding function to prevent the alloy from corroding. Specifically, the FeSiAl@C-300 °C delivers increased complex permeability and permittivity in the frequency range of 7–14 GHz, as well as improved impedance matching. In addition, the corrosion resistance is measured using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 5 wt% NaCl solution. The results indicate that the synthesized hybrid exhibits excellent corrosion resistance capability. So, the composite synthesis is a worthy approach to design hybrid materials for effective microwave absorption and corrosion resistance properties for practical applications. • FeSiAl@C were developed by decorating carbon layer through CCVD. • FeSiAl@C showed a better microwave absorption than FeSiAl. • Carbon layer provided the physicochemical protection for corrosion resistance properties of FeSiAl. [ABSTRACT FROM AUTHOR]