钴离子取代对Ca5Mg4–xCox(VO4)6陶瓷微波介电性能的影响

采用固相反应法制备低温烧结Ca₅Mg₄(VO₄)₆微波介质陶瓷,研究了Co掺杂取代Mg对微波介电性能的影响。结果表明:Co取代后样品形成了固溶体,导致烧结温度降低。当相对密度较低时,致密度主导着εr的变化;当相对密度较高时,εr主要受单位体积离子极化率的影响。此外,Co取代使得晶粒尺寸减小,进而促进了Q×f值的提升。由于τf与键能有着密切的联系,而V—O键的键能最大,τf随着V—O键键能的变化而改变。Ca5Mg4(VO₄)₆具有最佳的微波介电性能:εr=9.65,Q×f=54 685 GHz,τf=–55.3×10^–6℃^–1。

Effect of Co Substitution on Microwave Dielectric Properties of Ca5Mg4-xCox(VO4)6 Ceramics

Ca₅Mg₄(VO₄)₆ microwave dielectric ceramic was prepared by a solid-phase reaction method. Mg element in Ca₅Mg₄(VO₄)₆ ceramic was substituted by Co element in order to improve the microwave dielectric properties. The phase composition and microscopic morphology of the ceramics were determined by X-ray diffraction and scanning electron microscopy. Also, the internal laws of the microwave dielectric properties were analyzed via theoretical calculations, such as bond energy. The formation of solid solution after Co substitutioncan decrease the sintering temperature. The density dominates the change of εr at a higher relative density. However, εr is mainly affected by the ion polarizability per unit volume at a lower relative density. The grain size reduction caused by the substitution is beneficial to the promotion of the Q×f value. τf is closely related to the bond energy and changes with the bond energy of the V—O, which is the maximum bond energy in ceramics. Ca5Mg4(VO4)6 ceramic has the optimum microwave dielectric properties(i.e., εr=9.65, Q×f=54 685 GHz, and τf = –55.3×10^–6 ℃^–1).