Research on Rare Earth-Doped Zn1.8SiO3.8 Microwave Dielectric Ceramics and Their Applications in Filters

Abstract

Willemite is a low dielectric constant ceramic that is well suited for millimeter-wave applications. This study explores the improvement of the dielectric properties of Zn_1.8SiO_3.8 ceramics by doping with Nd₂O₃ at molar fractions of 2%, 4%, 6%, and 8%, with the goal of enhancing their application in microwave filters. The phase structure, morphology, and vibrational modes of the samples were analyzed by using XRD, SEM, Raman, and IR spectroscopy. Additionally, their dielectric constants, quality factors, and temperature coefficients were measured. The results indicate that the ceramic sample doped with 6 mol % Nd₂O₃ and sintered at 1225 °C maintains a stable dielectric constant and achieves a high Q × f value of approximately 130,000 GHz, exhibiting significantly enhanced dielectric properties compared to pure Zn_1.8SiO_3.8 ceramics. Based on the optimized Zn_1.8SiO_3.8 −6 mol % Nd₂O₃ ceramic system, a band-pass filter with a center frequency of 5.15 GHz and a bandwidth of 200 MHz was designed and fabricated. Experimental results demonstrate that the filter exhibits a low insertion loss of −0.62 dB and a return loss exceeding −20 dB, highlighting its strong potential for 5G communication applications. This study demonstrates the effectiveness of rare earth doping in optimizing the performance of microwave dielectric materials and provides new ideas for the design of high-performance dielectric filters.