CaCu₃Ti₄O12 (CCTO) is a potential dielectric material with giant permittivity, good stability over the wide temperature and frequency range. However, the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 10 ²–10⁶ Hz, which is far low to clarify the intrinsic dielectric feature. So, microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature (≤1000°C). Good microwave dielectric properties of permittivity ?? = 62.7, quality factor Qf = 3062 GHz and temperature coefficient of the resonant frequency τf = 179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C, the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry (DSC). This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics, but derives from composition segregation, liquid phase and defects associated with internal barrier layer capacitor (IBLC). It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.

随着当下5G和6G技术的高速发展，开发出具有适中的介电常数，较高的品质因数，接近0的谐振频率温度系数的陶瓷已是当下研究的重点。通过固相法制备Ca0.95-xCu0.05(Na0.5Bi0.5)xMoO4微波介质陶瓷，研究烧结温度和组分变化对陶瓷微波介电性能的影响。当烧结温度为640 ℃、x为0.5时综合微波介电性能较好，此时陶瓷的εr=15.8，Qf=21 361 GHz，τf= ?偉d3.8×10?偉d6/℃。通过X射线衍射仪、Raman光谱仪、扫描电子显微镜研究了微波介电性能变化的机理。Ca0.45Cu0.05(Na0.5Bi0.5)0.5MoO4陶瓷与Al电极共烧结果显示有较好的相容性，表明Ca0.95?偉dxCu0.05(Na0.5Bi0.5)xMoO4陶瓷具有作为低温共烧微波介质陶瓷材料的应用潜力。

为获得低介电损耗、高耐压强度的Al2O3基低温共烧陶瓷(LTCC)材料, 采用固相法制备了x(6La2O3·24CaO·50B2O3·20SiO2)(LCBS)+(1-x)Al2O3玻璃/陶瓷。通过X射线衍射仪、扫描电子显微镜、矢量网络分析仪、高压击穿试验仪、高温介电温谱仪对烧结样品的结构和性能进行了表征。结果表明: 添加适量的LCBS玻璃粉有助于提升材料的致密性、降低介电损耗、提高击穿场强。同时, 复阻抗谱分析表明, LCBS玻璃的加入可以显著提高玻璃/陶瓷的电阻率和活化能。当玻璃含量(摩尔分数)为44%时, 850 ℃烧结0.5 h, 可获得性能优异的LTCC陶瓷材料G44: εr=7.14, Q×f =5 769 GHz (f =13 GHz), Eb=57.44 kV/mm。

微波介质陶瓷是制造5G通信元件的关键材料, 采用传统的固相反应法制备BaSn(Si1-xGex)3O9(0≤x≤1.0)微波介质陶瓷, 研究Ge4+取代Si4+对BaSnSi3O9陶瓷烧结行为、晶体结构和微波介电性能的影响。结果表明: BaSnSi3O9陶瓷在最佳的 1 450 ℃烧结温度下表现出多孔的微观结构, 并呈现较差的微波介电性能(介电常数εr=6.61, 品质因数Q×f=7 977 GHz (谐振频率为15.03 GHz), τf=-37.8×10-6/℃)。通过Ge4+对Si4+的取代能形成BaSn(Si1-xGex)3O9固溶体, 其晶体结构为六方结构和P-6c2空间群。采用Ge4+对Si4+的取代促进了BaSn(Si1-xGex)3O9 (0≤x≤1.0)陶瓷的烧结, 改变了晶体结构参数实现对陶瓷微波介电性能的优化。BaSn(Si1-xGex)3O9(0≤x≤1.0)陶瓷的Q×f值主要与Si/Ge-O和Sn-O键中共价键的比例有关, 在x=1.0时BaSn(Si1-xGex)3O9陶瓷具有最优的微波介电性能: εr=8.53, Q×f=15 829 GHz (谐振频率为14.41 GHz), τf =-34.2×10-6 ℃-1。

为了更好的满足无线通讯高频化的要求, 采用固相法制备了温度系数近零的(1-x)MgNb2O6-xCaTiO3(x=0, 0.02, 0.04, 0.08, 0.12, 0.16)微波介质陶瓷。研究了CaTiO3的加入量对MgNb2O6微观结构和介电性能的影响, 探究各物相的形成和烧结行为。结果表明: 适当的CaTiO3加入量能够促进MgNb2O6的烧结, 降低了烧结温度。通过X射线衍射分析, CaTiO3与MgNb2O6在高温时会反应生成CaNb2O6和Ti8O15、Ti2Nb10O29。增加CaTiO3的加入量, 会降低陶瓷的品质因数Q×f, 但同时会提高其介电常数εr和频率温度系数τf。当CaTiO3的添加量x=0.16时, 样品在1 250 ℃烧结4 h后具有最佳的微波介电性能: εr=21.6, Q×f=86 601 GHz, τf=-7.3×10-6/℃。