Synthesis And Modification On The Dielectric Properties Of Zr_0.8Sn_0.2TiO₄ Microwave Dielectric Ceramics

The restriction for application in industrial production of Zr_0.8Sn_0.2TiO₄ microwave dielectric ceramics（ZST）was due to its high sintering temperature and difficulty in densifying.This paper aims in lowering the sintering temperature of ZST ceramic and improving its dielectric performance,What’s more,the influence mechanism of sintering aids in ZST ceramics were investigated and the modification methods were put forward.In the paper,thermal analysis and performance of samples was compared to explore the calcining process of ZST ceramics.ZST powders presintered for 2 h at 1150 ℃ can obtain better presintering powder.Cu²⁺,Zn²⁺,Bi³⁺ were doped in calcined powders to lower the sintering temperature of ZST,respectively.The influence of different valence state as well as the size of the cations on ZST ceramics were investigated.It was analysed from the relative density,oxygen structure,phase composition,morphology and microwave dielectric properties,coefficient of thermal expansion,etc.The ions whose radii close to Zr,Sn,Ti can enter in ZST lattice,resulting in oxygen octahedrons distortion and affect the order of ions.The ions can also generate the second phase.The combined action reduce the sintering temperature to 1075℃,1175℃,1200℃ for Cu²⁺,Zn²⁺,Bi³⁺,respectively.However,they caused deterioration in dielectric properties to diferrent degrees.The dielectric properties of Zn O doped ZST is the best among the dopings with εr = 39.58,Q·f = 32850 GHz,τf =-9.8ppm/℃.After determining the ZnO as the appropriate sintering aids,Sm₂O₃/ACO₃（A = Ba,Sr,Ca,Mg）were also doped to modify the dielectric properties of ZST ceramics.The mechanism of rare earth ions and alkaline earth ions on ZST of ceramics were explored.ZST phase is still the main phase.Ba²⁺,Sr²⁺,Ca²⁺ exsited in the octahedral gap,but Sm³⁺,Mg²⁺ replaced the cation,Sm³⁺ worked together with alkaline earth ions to influence the crystal structure.The best microwave dielectric ceramic performance was achieved by ZST ceramics doped with1wt%Sm₂O₃ and 1.0wt%SrCO₃:εr = 44.7,Q·f=56547.6GHz,τf = 4.1ppm/℃Using the ZST as the substrate,a rectangular microstrip patch antenna with central frequency at2.45 GHz was designed by HFSS software.The central frequency was influenced largely by the length of the patch.The return loss and VSWR were satisfied for application after optimization.The central frequency of the antenna located at 2.45 GHz with the patch length of 8.058 mm and the width of13.42 mm.