Research On The Forming And Properties Of ZnAl₂O₄-based Microwave Dielectric Ceramics By Digital Light Processing

ZnAl₂O₄-based microwave dielectric ceramics are ideal materials for 5G lens antennas due to their excellent microwave dielectric properties,good mechanical properties and low thermal expansion coefficient.However,the traditional methods are difficult to meet the requirements of 5G microwave devices for high precision,low power consumption,and complex structure.This article took ZnAl₂O₄-based ceramics as the research object,and prepared ZnAl₂O₄-based ceramic parts by digital light processing（DLP）technology.The effect of contents of dispersant,solid loading,amounts of photoinitiator and sintering temperature on the rheological and light curing properties of ceramic slurry and the properties of ceramics after sintering were studied.The main research work and results are as follows:（1）Preparation of 0.79ZnAl₂O₄-0.21TiO₂ ceramic slurry suitable for DLP technology with high solid content,low viscosity and good light curing properties.The best slurry formula and forming parameters for DLP forming were as follows:the ceramic slurry with 2.0 wt%dispersant had the best dispersion effect and good stability;the ceramic slurry with 30～45 vol%solid content could ensure good rheological properties;the ceramic slurry with 1.0 wt%photoinitiator had the best curing property;and when the range of energy dose was 110～160m J/cm²,the layer thickness was 50μm,the ceramic slurry had high single-layer curing depth and forming precision.（2）Preparation of 0.79ZnAl₂O₄-0.21TiO₂ ceramic by DLP technology.The two-step debinding method of atmospheric pyrolysis of organic and residual carbon treatment could ensure the integrity of the ceramic green body.The samples with solid loading of 40 vol%after sintering at 1500°C for 4 h showed the best properties:relative density is 95.29%,ε_r=11.55,Q×f=62266 GHz,τ_f=-0.64 ppm/℃.（3）Preparation of 90 wt%（0.75ZnAl₂O₄-0.25TiO₂）-10 wt%Mg TiO₃（ZTM）ceramic by DLP technology.ZTM ceramics had higher maximum densification rate(v_max=0.297 s^-1)and lower densification temperature(T_max=1335°C),and the formation of Mg Ti₂O₅ in the range of1120°C accelerated the densification rate in the local temperature region,and finally ZTM ceramics can complete densification after sintering at 1400°C for 3 h;TiO₂Mg Ti₂O₅precipitated from Mg Ti₂O₅ could react with ZnAl₂O₄ to form Mg Al₂O₄,which resulted in layered grains.ZTM ceramics after sintering at 1450°C for 3 h could obtain the optimum microwave dielectric properties:ε_r=12.99,Q×f=69245 GHz,τ_f=-9.50 ppm/°CBy optimizing the ceramic slurry formula,DLP forming parameters and sintering process,it is expected to realize the preparation of ZnAl₂O₄ based lens antenna with high performance by DLP technology,and promote the preparation and application of 5G microwave devices with precise structure.