化学计量比对镓酸镁尖晶石陶瓷微波介电性能的影响

尖晶石型微波介质陶瓷因高品质因数和可调的谐振频率温度系数在无线通信等领域应用广泛。本文通过无压烧结制备了MgO·nGa₂O₃(n=0.975、1.00、1.08和1.17)尖晶石陶瓷,采用XRD Rietveld全谱拟合研究了化学计量比对晶体结构的影响,并结合键价理论模型探究了微波介电性能与晶体结构的关系。结果表明:MgO·nGa₂O₃陶瓷相对介电常数(ε_r)的变化与晶格常数和离子极化率有关;品质因数(Q×f)受键强和阳离子有序度的共同影响,随n值增大从165 590 GHz下降至109 413 GHz;而谐振频率温度系数(τ_f)与晶体热膨胀系数相关。制备的MgO·0.975Ga₂O₃陶瓷具有优异的微波介电性能:ε_r=9.69、Q×f=165 590 GHz(频率14 GHz下)和τ_f=-7.12×10^-6/℃。

Influence of Stoichiometric Ratio on the Microwave Dielectric Properties of MgO·nGa2O3 Spinel Ceramics

Spinel-type microwave dielectric ceramics are widely applied in wireless communication due to its high quality factor and adjustable resonant frequency temperature coefficient. In this paper, MgO·nGa₂O₃ (n=0.975, 1.00, 1.08 and 1.17) spinel ceramics were prepared by pressureless sintering. The influence of stoichiometric ratio on the crystalline structure was studied by the XRD Rietveld whole pattern fitting method. The relationship between microwave dielectric properties and crystalline structure was explored through the bond valence theory model. The variation of relative dielectric constant (ε_r) of MgO·nGa₂O₃ ceramics is related to the lattice constant and ion polarizability. The quality factor (Q×f) decreases from 165 590 GHz to 109 413 GHz as n increases, which is affected by bond strength and the degree of cation order. The resonant frequency temperature coefficient (τ_f) is related to the crystal thermal expansion coefficient. The obtained MgO·0.975Ga₂O₃ ceramics possess excellent microwave dielectric properties: ε_r=9.69, Q×f=165 590 GHz (at 14 GHz) and τ_f=-7.12×10^-6/℃.