Ti-B位置换改性Mg2SiO4陶瓷微结构与微波介电性能研究

Ti-B位置换改性Mg2SiO4陶瓷微结构和微波介电性能的研究中发现,在合成Mg2SiO4陶瓷过程中,Mg2SiO3总是作为第二相出现,Ti的引入能够有效地抑制Mg2SiO3的出现.但Ti不是进入Si-O四面体取代置换Si形成Mg2(Si1-xTixO4固溶体,而是Mg与反应形成Mg2TiO4、Mg2Ti2O5等第二相.Mg2(Si1-xTix)O4陶瓷随着值x增加,介电常数εr从6.8增加到8.1,Qf值也获得显著改善,但谐振频率温度系数不会因Ti引入而得到优化.在x=0.1时,Mg2(Si0.9Ti0.1)O4陶瓷获得优良的微波介电性能:εr=7.4,Qf=73 760GHz,τf=60·10-6/℃.     

微波介质陶瓷

微波介质陶瓷作为广泛应用于微波谐振器、滤波器、介质基板、移相器等现代移动通信设备的核心材料,大大促进了现代通信事业的飞速发展。本文综述了近几十年来微波介质陶瓷的研究现状,以及各类体系微波介质陶瓷发展的最新进展,同时对微波介质陶瓷的发展趋势进行了讨论。     

高性能陶瓷微波介质材料

微波介质陶瓷可使微波通信和其他微波设备小型化,是有良好发展前景的一种介电材料。目前已经研制出许多具有高介电常数、高品质因数、低介质损耗及小谐振频率温度系数的优质微波介质陶瓷。本文综述近年来微波介质陶瓷在制备工艺、改良介电性能及应用方面的最新进展,并指出了今后的研究方向。     

Ca(Mg_(1–x)Co_x)Si_2O_6陶瓷的烧结性能与微波介电性能

通过Co2+对Mg2+的取代,探讨不同x值下Ca(Mg1–xCox)Si2O6陶瓷的物相组成、烧结性能、微观结构以及微波介电性能。结果表明:Co2+对Mg2+的取代,可将Ca(Mg1–xCox)Si2O6陶瓷的烧结温度从1300℃降低至1 175℃;Co2+在Ca(Mg,Co)Si2O6中的固溶极限在0.2~0.3之间,Mg2+在Ca(Co,Mg)Si2O6中的固溶极限在0.3~0.4之间,当x位于0.3~0.6之间时,出现Ca(Mg,Co)Si2O6与Ca(Co,Mg)Si2O6两相共存;无论是Co2+固溶入Ca Mg Si2O6,形成Ca(Mg,Co)Si2O6,还是Mg2+固溶进入Ca Co Si2O6,形成Ca(Co,Mg)Si2O6,陶瓷晶粒均随固溶度的增大,出现异常长大,进而恶化陶瓷的品质因数。当x=0.5时,Ca(Mg,Co)Si2O6与Ca(Co,Mg)Si2O6两相共存,有效细化了陶瓷晶粒尺寸,1 225℃烧结后,陶瓷的微波介电性能为εr=8.04,品质因数Q×f=59 108 GHz,谐振频率温度系数τf=–51.02×10–6/℃。     

低温烧结Mg4Nb2O9微波介质陶瓷

研究了V2O5对Mg4Nb2O9陶瓷的烧结温度、相结构和微波介电性能的影响.结果表明,添加1％～8％的V2O5,能使该陶瓷的烧结温度降低到1000～1050℃而对其微波介电性能的影响很小,材料的主晶相为有序型刚玉结构的Mg4 Nb2O9,存在Mg4Nb2O6和Mg5Nb4O15杂相而没有检测到V2O5的存在.陶瓷的密度对微波介电性能起着决定性作用,介电常数e1与密度成线性关系(在99.99％的置信限内,其相关系数为0.98252),Q·f值与密度的关系较复杂.添加1％的v2O5,将Mg4Nb2O9陶瓷的烧结温度降低到了1050℃,得到了εr=12.72,Q·f=151040GHz的优异性能.     

Effects of Ca/Ti Cosubstitution upon Microwave Dielectric Characteristics of CaSmAlO4 Ceramics

(Ca_{1+ x} Sm_{1− x} )(Al_{1− x} Ti _x )O₄ (0≤ x ≤0.4) ceramics were synthesized by solid-state reaction method and their microstructures and microwave dielectric properties were investigated. X-ray diffraction analysis and energy-dispersive X-ray analysis indicated that the matrix phase was a solid solution with a composition represented by the chemical formula (Ca_{1+ x} Sm_{1− x} ) (Al_{1− x} Ti _x )O₄ and minor amount of (Ca,Sm)(Al,Ti)O₃ secondary phase was detected. Ca/Ti cosubstitution could significantly improve the microwave dielectric characteristics of CaSmAlO₄ ceramics, and the excellent microwave dielectric characteristics were obtained in the modified ceramics as ɛ_r=19–23, Q × f =49 100–118 700 GHz, and τ_f=−15–15 ppm/°C.     

Effect of Zn/Si Ratio on the Microstructural and Microwave Dielectric Properties of Zn2SiO4 Ceramics

Zn₂SiO₄ ceramics synthesized by the conventional solid-state method exhibited a low Q × f value, possibly due to the formation of a ZnO second phase. However, with a small ZnO reduction from the Zn₂SiO₄ ceramics, the ZnO second phase disappeared and grain growth occurred due to the formation of a Si-rich liquid phase. Specimens with a large grain size exhibited an improved Q × f value. In particular, the ceramics with nominal composition Zn_1.8SiO_3.8 sintered at 1300°C exhibited improved microwave dielectric properties of ɛ_r=6.6, Q × f =147 000 GHz, and τ_f=−22 ppm/°C.     

添加TiO2对Mg4Nb2O9陶瓷的结构与性能的影响

Mg4Nb2O9具有与α-Al2O3相同的刚玉型晶体结构,可望成为新一代高Q、低ε基板材料.然而,该材料却具有很大的负谐振频率温度系数(τf=-7.05×10-5/℃),期望通过添加TiO2(τf=4.50×10-4/℃)以达到调整的目的.适量的添加TiO2将Mg4Nb2O9陶瓷的烧结温度降低了约100℃,并增强了陶瓷的性能,微波介电性能与其密度呈线性关系.由于添加的TiO2与Mg5Nb4O15反应形成了(Ng,Ti)5(Nb,Ti)4O15第二相,使得TiO2对该陶瓷τf值的调整作用不显著.1300℃、5h烧结添加质量分数为2.5%的TiO2的Mg4Nb2O9陶瓷具有最佳的性能:εr=13.61,Q·f=196620GHz,τf=-5.04×10-5/℃.     

低介电常数(Mg_(1–x)Y_x)_2Al_4Si_5O_(18)陶瓷的制备与微波介电性能

采用传统陶瓷固相反应烧结法制备(Mg1–xYx)2Al4Si5O18陶瓷。Y3+掺杂产生液相烧结作用,使得堇青石陶瓷的烧结温度从1 450℃降低到1 325℃。结果表明:(Mg1–xYx)2Al4Si5O18陶瓷在0≤x0.05范围内,以(Mg,Y)2Al4Si5O18固溶体形式存在;在0.05≤x0.25范围内,以Mg2Al4Si5O18/Y2Si2O7复相陶瓷形式存在。Y3+能够改善(Mg1–xYx)2Al4Si5O18陶瓷的颗粒尺寸分布,并使陶瓷的气孔率降低。(Mg1–xYx)2Al4Si5O18陶瓷的相对介电常数由x=0的6.15提高到x=0.05的6.31;然后逐渐降低至x=0.25的5.90。品质因数Qf值由x=0的33 000 GHz提高到x=0.05的41 000 GHz,然后降低至x=0.25的24 000 GHz。谐振频率温度系数(0.05≤x0.25)值从–32×10–6/℃提高到–24×10–6/℃。     

高介电常数微波介质陶瓷

近年来，微波介质陶瓷作为现代通信技术中关键的核心材料，广泛应用于微波谐振器、滤波器、介质基板、移相器等微波元器件，极大的促进了现化通信事业的飞速发展。本文综述了高介电常数微波介质陶瓷近几十年来的研究进展，并对高介电常数微波介质陶瓷的发展趋势进行了讨论和展望。     

微波介质陶瓷及其展望

综述了微波介质陶瓷材料的特性和发展现状，介绍了几种重要的微波介质陶瓷体系，讨论了微波介质陶瓷性能的影响因素，指出了改善其性能的途径和微波介质陶瓷的预期进展。     

Structure‐Dependent Microwave Dielectric Properties and Middle‐Temperature Sintering of Forsterite (Mg1–xNix)2SiO4 Ceramics

The crystal structure, microstructure, and microwave dielectric properties of forsterite‐based (Mg_1–xNi_x)₂SiO₄ (x = 0.02–0.20) ceramics were systematically investigated. All samples present a single forsterite phase of an orthorhombic structure with a space group Pbnm except for a little MgSiO₃ secondary phase as x > 0.08. Lattice parameters in all axes decrease linearly with increasing Ni content due to the smaller ionic radius of Ni²⁺ compared to Mg²⁺. The substitution of an appropriate amount of Ni²⁺ could greatly improve the sintering behavior and produce a uniform and closely packed microstructure of the Mg₂SiO₄ ceramics such that a superior Q × f value (152 300 GHz) can be achieved as x = 0.05. The τ_f value was found to increase with increasing A‐site ionic bond valences. In addition, various additives were used as sintering aids to lower the sintering temperature from 1500°C to the middle sintering temperature range. Excellent microwave dielectric properties of ε_r~6.9, Q × f~99800 GHz and τ_f~?50 ppm/°C can be obtained for 12 wt% Li₂CO₃‐V₂O₅‐doped (Mg_0.95Ni_0.05)₂SiO₄ ceramics sintered at 1150°C for 4 h.     

高介电常数微波介质陶瓷材料的研究现状

综述了微波介质陶瓷材料特性、影响因素及高介电常数微波介质陶瓷材料的发展现状,讨论了提高微波介质材料性能的途径.分别介绍三类高介电常数微波介质陶瓷的研究现状,并探讨了微波介质陶瓷今后的发展趋势.     

微波介质陶瓷的显微结构与性能

本介绍了显微结构中的一些主要因素对微波介质陶瓷性能的影响；重点分析了晶粒-主晶相、玻璃相、气孔以及缺陷对微波介质陶瓷性能的影响；通过选择适当的工艺方法，如掺杂、湿化学合成方法等，实现陶瓷结构的致密、均匀，从而提高陶瓷体的微波性能。     

微波介质陶瓷的研究进展

综述了微波介质陶瓷材料的特性和发展现状,给出了多数目前已经研究的微波陶瓷体系及其性能,阐述了其制备方法,提出了改善其性能的途径和微波介质陶瓷的预期进展.     

Forsterite Ceramics Based on Sol-Gel Powders

The sol-gel method is used to obtain highly dispersed sintering-active forsterite powders. These powders were used to produce sufficiently strong and dense ceramics without additives at a firing temperature of 1350°C, however, full sintering of forsterite is hampered by intense recrystallization.     

Doping Effects of Ta on Conductivity and Microwave Dielectric Loss of MgTiO3 Ceramics

Two kinds of solid solution systems of Ta-doped MgTiO₃ were identified by X-ray diffraction, which can be represented by the formulae MgTi_{1− x} (Mg_1/3Ta_2/3) _x O₃ (0≤ x <0.5) and MgTi_{1− x} Ta _x O₃ (0≤ x <0.05). The conductivity and microwave dielectric loss for the two solid solution systems were examined by AC impedance and microwave resonator measurements, respectively. In the system MgTi_{1− x} (Mg_1/3Ta_2/3) _x O₃, the mechanism for the solid solution formation is the isovalent substitution of for Ti⁴⁺. In the system MgTi_{1− x} Ta _x O₃, the doping mechanism is the aliovalent substitution of Ta⁵⁺ for Ti⁴⁺, where for a small amount Ta doping, the oxygen vacancies formed during the high-temperature preparation are filled by an extra oxygen introduced from Ta₂O₅ and further Ta doping leads to an increase in the contents of and electrons, which was consistent with conductivity measurements. In both systems, the Q × f values improved, e.g., ∼17% for the isovalent substitution at x =0.08 and ∼10% for the aliovalent substitution at x =0.02. The filling oxygen vacancy and the substitution of Ta/Mg for Ti may contribute to the improvement of Q × f values for both systems.     

Mg4(Mb2-xSbx)O9陶瓷的制备与微波介电性能

采用传统固相反应法制备了Mg4(Nb2-xSbx)O9陶瓷,研究了该材料的烧结性能、物相结构、显微组织和微波介电性能.X射线衍射结果显示,在x小于或等于1.6的范围内,形成了具有α-Al2O3刚玉型晶体结构的连续固溶体,晶轴长度和晶胞体积均随着锑含量的增加而降低.在x等于2.0时,Mg4Sb2O9的物相结构发生了变化,晶轴长度和晶胞体积也发生了突变.当0.4≤x≤O.8时,陶瓷的烧结温度从1400℃降低到了1300℃;而当x≥1.2后,陶瓷的烧结性能和微波介电性能均降低.在1300℃,5h的烧结条件下,Mg4(Nb1.6Sb0.4)O9陶瓷的微波介电常数(εr)为12.26,Q·f为168450 GHz.     

高介电常数微波介质陶瓷的发展及研究现状

对高介电常数微波介电陶瓷中的BaO-Ln2O3-TiO2、复合钙钛矿CaO2-Li2O2-Ln2O3-TiO2及铅基钙钛矿体系的发展及研究现状进行了概述,归纳了研究中存在的问题,同时对未来的发展趋势做了预测.对新型填满型钨青铜结构陶瓷也进行了简要的介绍,指出其具有良好的发展前景,但其介电弛豫性需要进一步的研究.     

Dielectric Measurements on High-Q Ceramics in the Microwave Region

The postresonator method proposed by Hakki and Coleman for the measurement of dielectric properties of solids in the microwave region is reexamined. Based on the experiments performed around 10 GHz, the limitations of the method in loss determination for materials with tan δ, 5 × 10⁻⁴ are outlined. Alternative techniques for studying high- Q materials are described. Loss measurements performed on well-prepared ceramics have been used to draw comparisons among these techniques. Some of the experimental findings are new and are reported for the first time.