Li2O–B2O3–SiO2–CaO–Al2O3 Research Articles

Li2O–B2O3–SiO2–CaO–Al2O3 glass-doped NiCuZn ferrite with high permeability and reliability for high-frequency MLCI application

Li2O–B2O3–SiO2–CaO–Al2O3 glass-doped NiCuZn ferrite with high permeability and reliability for high-frequency MLCI application

Temperature-stable and medium-high K of Ti/W co-doped M-phase LNT microwave ceramics for LTCC dielectric devices

The increasing demand for miniaturized electronic devices requires the development of advanced medium-high K materials. In this work, novel (Ti1/2W1/2)5+-substituted LiNb0.6-x(Ti1/2W1/2)xTi0.5O3 (LNT-xTW, 0 ≤ x ≤ 0.12) ceramics were successfully prepared by the solid-state method. The increase in TW content led to the formation of LNT-0.08 TW ceramic with medium-high K and high Q × f after sintering at 1050 °C. This ceramic also recorded improved characteristics with εr∼53.84, Q × f∼7482 GHz and τf∼43.43 ppm/°C related to ionic polarizability, large grains, high densification, and [Ti2O3]2+/N layers. In addition, Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) used as an effective sintering aid, improved densification and promoted sintering by not only decreasing the temperature to 900 °C, but also enhancing the microwave dielectric properties with εr∼49.46, Q × f∼8149 GHz, and τf∼12.04 ppm/°C. The Q × f value was estimated to 1.15 ∼ 2-fold higher than other LNT-based ceramics within stable τf. More encouragingly, the LNT-0.08 TW ceramic also showed good chemical match with Ag, suggesting usefulness for miniaturized LTCC devices.

Low loss and good chemical compatibility with silver electrodes of Cu2+-substituted Ba3Ti4Nb4O21 ceramics realizing low temperature co-fired ceramics technology: Crystal structure, vibration modes and chemical bonds studies

New low loss and low-sintering temperature co-fired Ba3-xCuxTi4Nb4O21 (BCTN, 0 ≤ x ≤ 0.12) ceramics with 0.60 wt% Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were prepared by solid-state reaction methodology. This work showed that CuO and LBSCA were effective sintering aid, which improved the densification and decreased sintering temperature. Thus, the excellent microwave dielectric properties of BCTN ceramics (x = 0.08) were obtained after sintering at 925 ℃ with εr ~ 44.18, Q×f ~ 17,860 GHz (@ 5.6 GHz) and τf ~ 94.76 ppm/℃. Q×f value was increased nearly 3-fold compared to pure BTN ceramics (~ 6090 GHz). Based on the P-V-L bond theory, the Ti-O and Nb-O bonds together contributed greatly to εr. The Nb-O bonds was the main factor affecting the internal loss on Q×f. The τf closely related to the oxygen octahedron [Ti1/Nb1O6]. The BCTN ceramics would not react with Ag electrodes, and had great potential to be used in LTCC microwave devices.

Effects of LBSCA glass addition on sintering behavior, Raman spectroscopy, and microwave dielectric properties of LiNb0.6Ti0.5O3 ceramics

In this study, LiNb0.6Ti0.5O3 (LNT) ceramics with x wt.% (0 ≤ x ≤ 2.0) of added Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass were prepared by conventional solid-state reaction method. Effects of LBSCA glass on phase composition, microstructure, lattice vibration, and microwave dielectric properties of the LNT-x wt.% LBSCA ceramics were investigated. X-ray diffraction analysis confirmed the formation of single-phase Li1.075Nb0.625Ti0.45O3 in all samples. Combined with Raman spectroscopy, it was suggested that the microwave dielectric properties were highly associated with the bulk density, the vibration damping behavior, the Nb–O bond strength, and the degree of order in crystal structure. Introduction of LBSCA glass resulted in effective decrease in the sintering temperature to 925 °C and contributed to the improvement of quality factor (Q × f) value. The LNT-0.4 wt% LBSCA sample sintered at 925 °C exhibited excellent microwave dielectric properties with ϵr = 62.9, Q × f = 7561 GHz, and τf = 12.56 ppm/°C coupled with good chemical compatibility with silver), which offers good application prospects in the field of low-temperature co-fired ceramic technology.

Enhanced magnetic properties of low temperature sintered LiZnTi ferrite ceramic synthesized through adjusting microstructure

The regulation strategy of microstructure, either through promoting grain growth or by improving compactness, is highly effective to improve magnetic properties of low temperature sintered ferrite ceramics. Until now, many studies emphasized grain growth, which often leads to deterioration in uniformity. In this work, a dense Bi2O3-substituted LiZnTi (Li0.43Zn0.27Ti0.13Fe2.167Bi0.003O4) ferrite with enhanced magnetic properties was obtained, using LBSCA (Li2O–B2O3–SiO2–CaO–Al2O3) additives (x wt.%, x = 0.00–0.40). Interestingly, SEM images revealed that the appropriate LBSCA glass not only can promote grain growth and enhance compactness of the Bi2O3-modified LiZnTi ferrite, but also can suppress abnormal grain by facilitating grain boundary diffusion. Moreover, the relationships between microstructural changes and magnetic properties of the LiZnTi ferrite have been discussed in detail. Finally, a compact LiZnTi ferrite with high saturation flux density (Bs = 319.2 mT), low coercivity (Hc = 213 A/m) and high saturation magnetization (σs = 69.5 emu/g) were synthesized when the 0.10 wt% LBSCA glasses were added and sintering temperature was ∼900 °C. Meanwhile, the ferrite samples modified with 0.20 wt% LBSCA glasses have uniform and compact grain (∼3.0 μm). Such a sintering strategy is expected to be a referential experience for other advanced ceramics.

Effects of Li2O–B2O3–SiO2–CaO–Al2O3 glass addition on the sintering behavior and microwave dielectric properties of Li3Mg2NbO6 ceramics

Li3Mg2NbO6 ceramics modified with Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass additives were densified below 950 °C via a solid-state route. Single orthorhombic phase and dense morphology were obtained with the LBSCA glass introduction. Promising microwave dielectric properties, especially with an improved Q × f value, were obtained in the Li3Mg2NbO6 ceramics with 0.5 wt% of the LBSCA glass addition sintered at 925 °C for 4 h: er = 15.16, Q × f = 90,557 GHz, τf = − 16.22 ppm/°C. It is suggested that the microwave dielectric performance was highly related to the densification, the polarizability, and the effects of the packing fraction. All experimental facts indicate that the LBSCA modified Li3Mg2NbO6 ceramics are potential candidates for Low-Temperature Co-fired Ceramic (LTCC) applications.

Temperature stability and chemical compatibility of novel Li1.6Zn1.6Sn2.8O8 ceramics

A new Li1.6Zn1.6Sn2.8O8 (LZS) ceramic with good temperature stability was synthesized by a simple solid-state reaction. The LZS ceramic exhibited nearly compact structure and possessed optimum dielectric characteristics of εr = 11.24, Q×f = 59800 GHz, τf = −7.86 ppm/°C. The influences of Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass additive on the microwave dielectric characteristics, structure composition and morphology of LZS ceramics were investigated. The results demonstrated that LBSCA glass could significantly reduce sintering temperature and then suppress the appearance of impure phase SnO2. The scanning electron microscope (SEM) results indicated that the microstructure evolution from flake-like to particle-like appeared with increasing LBSCA, which was accompanied by the decline in grain sizes from 2.66 μm to 0.55 μm. The εr and Q×f exhibited trends resemble that of apparent densities. The variation of τf mainly originated from the large and negative τf of LBSCA glass. Particularly, the LZS-1.2 wt% LBSCA ceramic obtained at 925 °C displayed a compact and uniform microstructure and possessed optimum microwave dielectric characteristics of εr = 10.51, Q×f = 31700 GHz, τf = -7.93 ppm/°C. Moreover, LZS-1.2 wt% LBSCA ceramic exhibited favorable compatibility with silver, endowing the material with possible application in low temperature co-fired ceramic (LTCC).

Effects of Zn2+ substitution on the sintering behaviour and dielectric properties of Li2Mg1−xZnxSiO4 ceramics

Silicates, the basis on which low-temperature-fired dielectric materials widely studied for applications in the fields of microwave integrated circuits, have been developing vigorously owing to their low dielectric constants and tangent loss values. In this work, Zn2+ was gradually substituted to Mg2+ to make the sintering temperature decreased and enhance the microwave dielectric properties of Li2MgSiO4. Li2Mg1−xZnxSiO4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) powders were prepared through solid-state reaction. Aiming to decrease the sintering temperature to approximately 900 °C, 3 wt% Li2O–B2O3–SiO2–CaO–Al2O3 glass was used as a sintering aid. The XRD patterns made it clear that the major crystalline phase of the materials was Li2(Mg,Zn)SiO4. A new unexpected crystalline phase of ZnxSiO4 appeared when the amount of Zn2+ substituted increased to more than 0.4. SEM micrographs demonstrated that when x = 0.4, the most homogeneous microstructure appeared. Meanwhile, the Q × f value and the relative density also reached to their peaks when x = 0.4, respectively. Moreover, 3 wt% LBSCA-doped Li2Mg0.6Zn0.4SiO4 ceramics exhibited excellent dielectric properties of er = 5.89, Q × f = 44,787 GHz and τf = − 71.65 ppm/°C when sintered at 900 °C. The material exhibited low relative permittivity and low dielectric loss and could thus be a potential candidate for LTCC device applications.

Structure and microwave dielectric behaviour of low-temperature-fired Li2Zn1−xCoxTi3O8 (x = 0–0.07) ceramics for low temperature co-fired ceramic applications

Low-temperature-fired Li2Zn1−xCoxTi3O8 (x = 0, 0.03, 0.04, 0.05, 0.06, 0.07) ceramics with 1.5 wt% Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass as sintering aid were attained through a traditional solid-state-reaction method, and the relationship between their structures and microwave dielectric properties were thoroughly investigated. X-ray diffraction patterns revealed that the solid solutions composed of Li2ZnTi3O8 and Li2CoTi3O8 were produced. The main peaks were identified with the cubic spinel phase of the Li2(Zn,Co)Ti3O8. Co substitution successfully lowered the sintering temperature of Li2ZnTi3O8 to approximately 900 °C and accelerated its densification when LBSCA glass was used as the sintering aid. The cobalt content considerably influenced grain homogeneity, grain size and dielectric polarizability, as well as the variation in relative permittivity (er) and quality factor (Q × f). When x = 0.04, Li2Zn0.96Co0.04Ti3O8 ceramic sintered at 900 °C had the most uniform grain size and exhibited optimum microwave dielectric properties, having a relative permittivity of 21.61, Q × f of 79,100 GHz and temperature coefficient of resonance frequency (τf) of − 12.3 ppm/°C. Thus, it showed potential for low temperature co-fired ceramic applications.

Microwave dielectric properties of low-temperature-fired LiAlO2–Li2TiO3 composite ceramics with near-zero temperature coefficient

A series of LiAlO2–Li2TiO3 ceramics with near-zero temperature coefficient of resonant frequency was obtained by using a solid-state method in this study. Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass was used to lower the sintering temperature of the ceramics to approximately 900 °C. Scanning electron microscope images illustrated the dense microstructures of the LiAlO2–Li2TiO3 ceramics when amount of LBSCA glass content exceeded 1.0 wt%. X-ray diffraction analyses indicated that LiAlO2 and Li2TiO3 were presented as separate phases in the composites and no any secondary phase was observed in the sintered samples. High-performance microwave dielectric properties with permittivity of ∼ 15.4, Q × f value of ∼ 52,740 GHz and τf value of ∼ + 1.37 ppm/°C were observed in the LiAlO2–Li2TiO3 ceramic sample sintered at 900 °C with 1.5 wt% LBSCA glass. The ceramic also exhibited excellent chemical compatibility with Ag, which indicated that the fabricated material could be a good candidate for low-temperature co-fired ceramic applications.

Microwave dielectric properties of the low-temperature-fired Li2ZnTi3O8–Li2TiO3 ceramics for LTCC applications

In this work, 0.73Li2ZnTi3O8–0.27Li2TiO3 ceramics were prepared through a traditional solid-state process. The effects of Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass addition on phase formation, microstructure, sintering characteristic and microwave dielectric properties of the ceramics were investigated. A small amount of LBSCA glass addition significantly reduced sintering temperature of the ceramics. X-ray diffraction analysis revealed that Li2ZnTi3O8 and Li2TiO3 phases coexisted without producing any other crystal phases in the sintered ceramics. Dielectric constant and Qf values were related to the amount of LBSCA addition and sintering temperatures. The specimens obtained near-zero temperature coefficient (τf) values through the compensation on the positive τf of Li2TiO3 and the negative τf of Li2ZnTi3O8. The 0.73Li2ZnTi3O8–0.27Li2TiO3 ceramic with 0.75 wt% LBSCA addition and sintered at 900 °C for 3 h exhibited excellent microwave dielectric properties of ɛr = 23.907, Qf = 63050 GHz and τf = 1.2 ppm/°C, which was very suitable for LTCC (low temperature co-fired ceramics) applications.

Influence of partial cobalt-ion substitution on the microstructure and dielectric properties of (Zn0.7Mg0.3)1-xCoxTiO3 ceramics

In this study, cobalt-ion substitution was applied to improve the microstructure and microwave dielectric properties of (Zn0.7Mg0.3)1-xCoxTiO3 ceramics. (Zn0.7Mg0.3)1-xCoxTiO3 ceramics were obtained via the conventional solid-state route, and Li2O:B2O3:SiO2:CaO:Al2O3 (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)TiO3 was the main crystalline phase. Scanning electron microscopy showed that proper cobalt-ion substitution promoted the densification and homogeneity of crystal grains in the (Zn0.7Mg0.3)1-xCoxTiO3 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 εr = 21.602, Q×f = 80,040 GHz and τf = −70.24 ppm/°C.

Li2O-B2O3-SiO2-CaO-Al2O3 and Bi2O3 co-doped gyromagnetic Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics for LTCC Technology

A modified low-temperature liquid phase sintering technique was attempted to fabricate Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics with a compact structure and improved properties through the solid-state reaction route. Fixed amount of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass was added to Li0.43Zn0.27Ti0.13Fe2.17O4 powders to decrease the sintering temperature below 950°C, while the addition of Bi2O3 oxide contributed to optimizing the microstructure and improving the magnetic and gyromagnetic properties. Selected parameters including saturation magnetization (Ms), coercivity (Hc) and ferromagnetic resonance line width (ΔH) were investigated as a function of doping content, and their relationships with porosity and microstructure were also discussed. The sample resintered at 940°C with co-doping of 0.3wt% of LBSCA glass and 0.03wt% of Bi2O3 presented excellent magnetic and gyromagnetic properties of Ms =73.32emu/g, Hc =120 A/m and ΔH=163Oe, suggesting that it is promising in the LTCC phase shifter fabrications.

Microwave dielectric properties of CaWO4–Li2TiO3 ceramics added with LBSCA glass for LTCC applications

In this work, 0.86CaWO4–0.14Li2TiO3 ceramics were prepared via a traditional solid-state process. The effects of Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) addition on the phase formation, sintering character, microstructure and microwave dielectric properties of the ceramics were investigated. A small amount of LBSCA addition could effectively lower the sintering temperature of the ceramics. X-ray diffraction analysis revealed that CaWO4 and Li2TiO3 phases coexisted without producing any other crystal phases in the sintered ceramics. The dielectric constant and Qf values were related to the amount of LBSCA addition and sintering temperatures. All specimens could obtain near-zero temperature coefficient (τf) values through the compensation of the positive τf of Li2TiO3 and the negative τf of CaWO4. The 0.86CaWO4–0.14Li2TiO3 ceramic with 0.5wt% LBSCA addition and sintered at 900°C for 3h exhibited excellent microwave dielectric properties of εr=12.43, Qf=76,000GHz and τf=−2.9ppm/°C.

Low-temperature-sintering characteristic and microwave dielectric properties of (Zn0.7Mg0.3)TiO3 ceramics with LBSCA glass

(Zn0.7Mg0.3)TiO3 (ZMT) powders were synthesized by a traditional solid-state preparation process. Meanwhile, the effects of adding Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass on the microstructure, phase formation, and microwave dielectric properties of ZMT ceramic were investigated. The LBSCA glass as a sintering agent can effectively reduce the sintering temperature of ZMT ceramic from 1100°C to 900°C, which can be attributed to its liquid-phase effect. Only 0.5wt% LBSCA-doping contributed to a 20.2% increase in relative density. XRD patterns indicated that ZnTiO3 was the major crystalline phase. Scanning electron microscopy images demonstrated that low LBSCA-doping (≤2.5wt%) promoted the grain densification and uniformity of specimens. A dense microstructure with uniform grain size could be obtained with 1wt% LBSCA and sintered at 900°C. The ceramic also exhibited excellent microwave dielectric properties: εr=21.6; Q×f=62,000GHz; and τf=−60ppm/°C.

Low temperature sintering and microwave dielectric properties of the LBSCA-doped (Zn0.95Co0.05)2SiO4 ceramics

The (Zn0.095Co0.05)2SiO4 powers were fabricated through a traditional solid-state preparation process. Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass was successfully developed as a low-doped sintering aid and it was found that LBSCA glass could significantly lower the sintering temperature of the synthesized powers from 1,300 °C to around 900 °C. Only 1 wt% of LBSCA-doping contributed to a 24.9 % increase of the relative density. X-ray diffraction spectra indicated that pure willemite phase was obtained. Scanning electron microscope images demonstrated that low LBSCA-doping (≤2 wt%) promoted the grain densification and uniformity of the specimens. A dense microstructure with uniform grain size could be obtained with 2 wt% LBSCA and sintered at 900 °C. The specimen also presented high microwave dielectric properties: er = 6.5, Q × f = 57,000 GHz and τf = −55 ppm/°C.

Enhanced ferromagnetic properties of low temperature sintering LiZnTi ferrites with Li2O–B2O3–SiO2–CaO–Al2O3 glass addition

The effects of Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass on the ferromagnetic properties of low-temperature sintered LiZnTi ferrites were systematically investigated. We characterized and analyzed the variation in microstructure, bulk density, porosity and ferromagnetic properties of the samples along with the changes of LBSCA glass content. The results revealed that the densification process of the samples was sensitive to the LBSCA glass content, and low LBSCA glass content was a precondition for sufficient densification, grain growth and ferromagnetic properties. The ferromagnetic resonance (FMR) linewidth (ΔH) was explained on the basis of spin wave theory of anisotropy and porosity broadening in polycrystalline materials. The sample sintered at 900°C with 0.85wt% LBSCA glass addition exhibits a saturation magnetization (ms) of 64.23emu/g and a ferromagnetic resonance (FMR) linewidth (ΔH) of 191Oe, suggesting that it is promising for LTCC phase shifters.

Low-temperature sintering and microwave dielectric properties of (Zn1−xCox)2SiO4 ceramics

(Zn1−xCox)2SiO4 (0≤x≤0.1) powders were synthesized by the traditional solid-state process. Fixed amount of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA)glass was added to (Zn1−xCox)2SiO4 powders to decrease the sintering temperature around 900°C. The X-ray diffraction (XRD) diffraction spectra indicated that there was no second phase formed while the Scanning Electron Microscope (SEM) images demonstrated that moderate Co-substitution contributed to the grain densification and uniformity in (Zn1−xCox)2SiO4 system. Moreover, the microwave dielectric properties strongly depended on the substitution content and sintering temperature. When sintered at 900°C, the sample with 0.05 Co substitution presented a compact microstructure with uniform grains and high microwave dielectric properties: εr=6.5, Q×f=57,000GHz and τf=−55ppm/°C.

Low Temperature Sintering of (Ca<sub>0.9375</sub>Sr<sub>0.0625</sub>)<sub>0.25</sub>(Li<sub>0.5</sub>Sm<sub>0.5</sub>)<sub>0.75</sub>TiO<sub>3</sub> Microwave Dielectric Ceramics

The sintering behavior and microwave dielectric properties of the (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (CSLST) ceramics doped with different amounts of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were investigated. The sintering temperature of the CSLST ceramics can be effectively reduced over 200oC due to the addition of LBSCA glass. For the 5 wt% LBSCA-doped CSLST ceramics, which are sintered at only 1000 oC for 5 h, show optimum microwave dielectric properties as follows: εr=84.74, Qf=2446 GHz and τf=-12.48 ppm/oC.

Low-Fire Processing of Voltage-Tunable Ba0.6Sr0.4TiO3 Dielectric

By adding a low-softening-point Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass, the voltage-tunable Ba0.6Sr0.4TiO3 (BST64) ceramics can be densified at 900 °C, which is 400–500 °C lower than the temperature for producing the pure BST64. This is caused by liquid-phase sintering and an interfacial reaction taking place at the interface of LBSCA/Ba0.6Sr0.4TiO3. For the samples with 10–35 vol % LBSCA glass, a high relative sintered density of >95% is obtained at 900 °C and the resulting dielectric composites have a dielectric constant and loss at 1 MHz in the ranges of 1040–145 and 0.4–1.0%, respectively. The voltage tunability of the resulting LBSCA+BST64 dielectric at 1 MHz and 1 kV/mm is in the range of 0.8–8%, which exhibits a decreasing trend with increasing LBSCA content.