Effects of SrO–B2O3–SiO2 glass additive on dielectric properties of Ba(Fe0.5Nb0.5)O3 ceramics

SrO–B₂O₃–SiO₂ (SBS) glass powders were prepared and employed as sintering aids to reduce the sintering temperature of Ba(Fe_0.5Nb_0.5)O₃ (BFN) ceramics. The effects of glass content on the dielectric properties and breakdown strength of BFN ceramics have been investigated. The volume density characterization results of (1 ? x) BFN ? x SBS ceramics indicate that the sintering temperature of BFN ceramics decreased by 200–350 °C with SBS glass addition (when x = 0, 0.01, 0.03 and 0.05). The XRD patterns show BFN ceramics indicate cubic crystal structure and without the formation of a secondary phase. The dielectric constant and dielectric loss decreased gradually with increasing glass content, and the dielectric loss decreased by one order of magnitude with SBS glass addition (when x = 0.05). The breakdown strength of (1 ? x) BFN ? x SBS ceramics increase with increasing glass content, in which is about 33.90 kV/cm with SBS glass addition (when x = 0.05). These improvements in the dielectric characteristics of BFN ceramics have great scientific significance for their applications.     

Effects of SrO–B2O3–SiO2 glass additive on densification and energy storage properties of Ba0.4Sr0.6TiO3 ceramics

SrO–B₂O₃–SiO₂ glass powders were prepared and employed as sintering aids to reduce the sintering temperature of Ba_0.4Sr_0.6TiO₃ ceramics. The effects of glass content and sintering temperature on the densification, dielectric properties and energy storage properties of Ba_0.4Sr_0.6TiO₃ ceramics have been investigated. The relative density characterization results indicate that densification of Ba_0.4Sr_0.6TiO₃ ceramics with glass content becomes apparently from sintering temperature of 1,060 °C. XRD results show all Ba_0.4Sr_0.6TiO₃ ceramics exhibit a perovskite structure without the formation of a secondary phase. The dielectric constant and dielectric loss decreased gradually with increasing glass content. The relationship between dielectric constant and breakdown strength was discussed using the thermochemical model. A discharged energy density of 0.44 J/cm³ with an energy efficiency of 67.4% was achieved for Ba_0.4Sr_0.6TiO₃ ceramic with 2.0 wt% glass addition sintered at 1,180 °C.     

Effects of Li2O3–B2O3–SiO2 addition on dielectric properties and microstructure of MgO–TiO2–ZnO–CaO ceramics

The effect of Li₂O₃–B₂O₃–SiO₂ (LBS) liquid-phase additives on the sintering, microstructures, and dielectric properties of MgO–TiO₂–ZnO–CaO (MTZC) ceramics was investigated. It was found that the sintering temperature could be lowered easily, and the dielectric properties of MTZC ceramics could be greatly improved by adding a small amount of LBS solution additives. With the addition of 10 wt% LBS, the ceramics sintered at 900 °C showed favorable dielectric properties with ε_r = 21.7, Qf = 5.0 × 10⁴ GHz, and TCF = ?21.6 ppm/ °C. The distructive physical analysis showed an excellent co-firing interfacial behavior between the MTZC ceramic and the Ag electrode. It indicated that MTZC ceramics with LBS solution additives have a number of potential applications on passive integrated devices based on the low-temperature co-fired ceramics technology.     

Effect of La2O3 additive on the dielectric properties of barium strontium titanate glass–ceramics

The barium strontium titanate (Ba_xSr_1–xTiO₃) glass–ceramics doped with different content of La were prepared via controlled crystallization. Phase compositions, microstructure and dielectric behaviors were investigated systematically. The results revealed that La₂O₃ additives had little influence on the dielectric constant but significantly changed the microstructure of the glass–ceramics, which led to improved breakdown strength (BDS). The optimized energy-storage density of 3.18 J/cm³ was achieved in the glass–ceramics with 1.0 wt% La₂O₃ content which is 2.56 times higher than pure BST glass–ceramics, suggesting glass–ceramics of this composition could be an attractive candidate for energy-storage applications.     

Effects of glass components on crystallization and dielectric properties of BST glass–ceramics

Crystallization behavior was studied for glass powders in which some portions of AlF₃ in the net composition of 60(Ba_0.7Sr_0.3)TiO₃–25SiO₂–15AlF₃ were replaced with Ga₂O₃ or Bi₂O₃. The replacement with Ga₂O₃ resulted in a progressive increase in crystallization temperature, which effectively assisted the viscous sintering of glass powders to produce densified BST glass–ceramics at relatively lower temperatures. For the Bi₂O₃-replaced glass powders, an increasing amount of Bi₂O₃ replacement lowered the crystallization temperature and yielded less densified glass–ceramics containing a considerable amount of glassy phase. The temperature dependence of permittivity was estimated for the Ga₂O₃- and Bi₂O₃-replaced glass–ceramics as a function of sintering conditions and the amount of replacement, respectively.     

Low temperature cofirable Li2Zn3Ti4O12 microwave dielectric ceramic with Li2O–ZnO–B2O3 glass additive

The effects of Li₂O–ZnO–B₂O₃ (LZB) glass additive on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Li₂Zn₃Ti₄O₁₂ ceramics were investigated. The addition of a small amount of LZB glass can reduce the sintering temperature of Li₂Zn₃Ti₄O₁₂ ceramics from 1,075 to 900 °C without much degradation of the microwave dielectric properties. Only a single-phase Li₂Zn₃Ti₄O₁₂ is formed in Li₂Zn₃Ti₄O₁₂ ceramic with LZB addition. Typically, the 1.5 wt% LZB glass-added Li₂Zn₃Ti₄O₁₂ ceramic sintered at 900 °C for 2 h can reach a high relative density of 97.5 % and exhibits good microwave dielectric properties, i.e., relative dielectric constant (ε _r ) = 19.1, quality factor (Q) = 7083.5 at 9 GHz, and temperature coefficient of resonant frequency (τ _f ) = ? 48.9 ppm/°C. In addition, the ceramic could be co-fired well with an Ag electrode, which is made it as a promising dielectric ceramic for low temperature co-fired ceramics technology application.     

Microstructure and microwave dielectric characteristics of CaO–B2O3–SiO2 glass ceramics

CaO–B₂O₃–SiO₂ (CBS) glass powders are prepared by traditional glass melting method, whose properties and microstructures are characterized by Differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that the pure CBS glass ceramics possess excellent dielectric properties (ε _r = 6.5, tan δ = 5 × 10⁻³ at 10 GHz), but a higher sintering temperature (>900 °C) and a narrow sintering temperature range (about 10 °C). The addition of a low-melting-point CaO–B₂O₃–SiO₂ glass (LG) could greatly decrease the sintering temperature of CBS glass to 820 °C and significantly enlarge the sintering temperature range to 40 °C. The CBS glass ceramic with 30 wt% LG glass addition sintered at 840 °C exhibits better dielectric properties: ε _r ≈ 6, tan δ < 2 × 10⁻³ at 10 GHz, and the major phases of the sample are CaSiO₃, CaB₂O₄ and SiO₂.     

Microwave dielectric properties of Ba2Ti3Nb4O18 ceramic doped with ZnO–B2O3–SiO2 glass and its compatibility with silver electrode

The effects of ZnO–B₂O₃–SiO₂ glass (ZBS) additions on the sintering behavior and microwave dielectric properties of Ba₂Ti₃Nb₄O₁₈ ceramic have been investigated. Due to the liquid phase effects resulting from the additives, the addition of ZBS glass can reduce the sintering temperature of Ba₂Ti₃Nb₄O₁₈ ceramic from 1,250 to 925 °C and induce no obvious degradation of the microwave dielectric properties. Typically, when 3wt% ZBS is added, a dense ceramic can be sintered at 925 °C with a ε_r of 33.2, a high of Q × f of 13,600 GHz and a low τ _f of −5.9 ppm/°C. Moreover, ZBS glass-added Ba₂Ti₃Nb₄O₁₈ ceramic has a chemical compatibility with silver electrode, which suggests that the ceramic could be applied to LTCC devices application.     

Improved microwave dielectric properties of Mg4Nb2O9 ceramics with CaO–B2O3–SiO2 glass additions

The effects of CaO–B₂O₃–SiO₂ (CBS) glass addition on the sintering temperature and dielectric properties of Mg₄Nb₂O₉ ceramics have been investigated using X-ray diffraction, Scanning electron microscopy and Differential thermal analysis. The CBS glass can change to liquid phase at about 750 °C and a small amount of CBS glass addition to Mg₄Nb₂O₉ ceramics can greatly decrease the sintering temperature to about 1,125 °C. It is revealed that the reduced sintering temperature is attributed to the formation of liquid phase. The major phases of the sample are Mg₄Nb₂O₉ and MgNb₂O₆. The relationship between τ _f values and the content of glass additions have the reverse change trends. The Mg₄Nb₂O₉ ceramics with 2wt% glass addition sintered 1,125 °C exhibit good microwave dielectric properties: dielectric constant (ε _r ) of 13 and Q·f value of 69,000 GHz.     

Effects of MnO2 doping on microstructure and microwave dielectric properties of Ba4.2Nd9.2Ti18O54–NdAlO3 ceramics

MnO₂ doped Ba_4.2Nd_9.2Ti₁₈O₅₄–NdAlO₃(13 wt%) (BNT–NA) microwave dielectric ceramics with the near zero τ _f and the wide range of sintering temperature were prepared by conventional solid state method. The effects of Mn⁴⁺ doping on the microstructures and microwave dielectric properties of BNT–NA ceramics were investigated. XRD patterns showed only a single BaNd₂Ti₅O₁₄ phase was identified in all samples and there was no second phase. The sintering temperature decreased from 1,380 to 1,320 °C as MnO₂ content increased from 0.1 to 0.9 wt%. The MnO₂ doped BNT–NA ceramics could be densified at a lower sintering temperature. The MnO₂ additive had a positive effect on lowing sintering temperature of BNT–NA ceramics. The τ _f varied from negative to positive with the increase of MnO₂. Excellent microwave dielectric properties were achieved in Ba_4.2Nd_9.2Ti₁₈O₅₄–NdAlO₃ ceramics doped with 0.3 wt% MnO₂ and sintered at 1,380 °C for 2 h: ε _r  = 66.5, Q × f = 13,948 GHz, τ _f  = 0.4 ppm/°C.     

Effects of MgO on properties of Li2O–Al2O3–SiO2 glass–ceramics for LTCC applications

Li₂O–Al₂O₃–SiO₂ (LAS) glass–ceramics for low temperature co-fired ceramics (LTCC) application were prepared by melting method, and the effects of MgO on the sinterability, microstructure, dielectric property, thermal expansion coefficient (CTE) and mechanical character of this glass–ceramics have been studied. The X-ray diffraction images represent that the main phase is β-spodumene solid solutions. And some ZrO₂ and CaMgSi₂O₆ phases in LAS glass–ceramics are detected. The LAS glass–ceramics without additive (MgO) sintered at 800° had the dielectric properties: dielectric constant (ε_r) of 5.3, dielectric loss (tanδ) of 2.97 × 10^?3 at 1 MHz, CTE value of 1.06 × 10^?6 K^?1, bulk density of 2.17 g/cm³, and flexural strength of 73 MPa. 5.5 wt% MgO-added LAS glass–ceramic achieves densification at 800° exhibited excellent properties: low dielectric constant and loss (ε_r = 7.1, tanδ = 2.02 × 10^?3 at 1 MHz), low CTE (2.89 × 10^?6 K^?1), bulk density = 2.65 g/cm³ as well as high flexural strength (145 MPa). The results indicate that the addition of MgO is helpful to improve the dielectric and mechanical properties. The formation of CaMgSi₂O₆ crystal phase with higher CTE leads to the increase of CTE value of LAS glass–ceramics due to the increasing MgO content, and the increase of CTE is favourable for matching with silicon (3.1 × 10^?6 K^?1). The prepared LAS glass–ceramics have the potential for LTCC application.     

Influence of La–B–Zn glass on the sintering and microwave dielectric properties of Ca–Nd–Ti ceramics

The effects of La₂O₃–B₂O₃–ZnO (LBZ) glass on the sintering behaviors, phase structures, microstructures and the microwave dielectric properties of perovskite type Ca_0.6Nd_0.26TiO₃ (CNT) ceramics were studied. It indicates that the LBZ glass has an obvious effect on lowering the sintering temperature without damaging the microwave dielectric properties of the CNT ceramics. Small amounts of LBZ glass significantly lowered the sintering temperatures of CNT ceramics and obtained excellent microwave dielectric properties. However, too much LBZ glass is leading to inferior dielectric properties. The CNT ceramics doped with 3 wt% LBZ can be well sintered at 975 °C for 4 h and shows good properties: ε_r = 87.87, Q × f = 8132 GHz (f = 3.3 GHz), τ_f = +244.63 ppm/°C.     

Influence of Al2O3/SiO2 ratio on the microstructure and properties of low temperature co-fired CaO–Al2O3–SiO2 based ceramics

In this work, in order to obtain the materials for low temperature co-fired ceramics applications, CaO–Al₂O₃–SiO₂ (CAS) based ceramics were synthesized at a low sintering temperature of 900 °C. The influences of Al₂O₃/SiO₂ ratio on the microstructure, mechanical, electrical and thermal properties were studied. According to the X-ray diffractomer and scanning electron microscopy results, the addition of the Al₂O₃ is advantageous for the formation of the desired materials. Anorthite(CaAl₂Si₂O₈) is the major crystal phase of the ceramics, and the SiO₂ phase is identified as the secondary crystal phase. No new crystal phase appears in the ceramics with the increasing Al₂O₃ content. More or less Al₂O₃ addition would all worsen the sintering, mechanical and dielectric properties of CAS based ceramics. The ceramic specimen (Al₂O₃/SiO₂ = 20/18.5) sintered at 900 °C shows good properties: high bending strength = 145 MPa, low dielectric constant = 5.8, low dielectric loss = 1.3 × 10^?3 and low coefficient of thermal expansion value = 5.3 × 10^?6 K^?1. The results indicate that the prepared CAS based ceramic is one of the candidates for low temperature co-fired ceramic applications.     

Low temperature sintering and dielectric properties of Li2ZnTi3O8–TiO2 composite ceramics doped with CaO–B2O3–SiO2 glass

The effects of CaO–B₂O₃–SiO₂ (CBS) glass addition on the sintering temperature and dielectric properties of Li₂ZnTi₃O₈–TiO₂ (LZT) composite ceramics have been investigated. Due to the compensating effect of rutile TiO₂ (τ_f ≈ +450 ppm/ °C), the temperature coefficient of resonant frequency (τ_f) for Li₂ZnTi₃O₈ + 4 wt% TiO₂ with biphasic structure was adjusted to a value near zero. The pure LZT ceramics were usually sintered at high temperature of about 1,160 °C. It was found in our experiment that a small amount of CBS glass additives could effectively lower the sintering temperature of LZT ceramics to 900 °C. With increasing the content of CBS glass, both of dielectric constant (ε_r) and quality factor (Q × f) value decreased. Typically, the 1 wt% CBS glass added Li₂ZnTi₃O₈ + 4 wt% TiO₂ ceramic sintered at 900 °C for 4 h exhibited good microwave dielectric properties of ε_r = 26.9, Q × f = 23,563 GHz and τ_f = ?1.5 ppm/ °C, which made it promising for low temperature co-fired ceramics technology application.     

Effects of binary additives B2O3–Y2O3 on the microstructure and thermal conductivity of aluminum nitride ceramics

Aluminum nitride (AIN) ceramics, with binary additives B₂O₃-Y₂O₃, were sintered at temperatures from 1700 to 1850 °C. The microstructure and sintering characteristics were studied by XRD, HREM, SEM and TEM/EDS, which showed that Y₂O₃ gave different yttrium aluminates through the reaction with Al₂O₃ under different conditions. With the increase of sintering temperature, the yttrium-to-aluminum atomic ratio Y/Al decreased in the secondary phases of the sintered bodies. It was discovered that B₂O₃ could dissolve in the yttrium aluminates, forming some ordered structure with a superlattice. After sintering at 1850 °C for 4 h, a specimen with a fine microstructure and a thermal conductivity of 190 Wm^–1K^–1 was obtained.     

Effect of TiO2 on the sintering temperature and dielectric properties of Li2O–MgO–ZnO–B2O3–SiO2 ceramic composites for LTCC applications

Journal of Materials Science: Materials in Electronics - The effects of injecting TiO2 to a Li2O–MgO–ZnO–B2O3–SiO2 (LMZBS) microwave dielectric composite on sinterability,...