Study Of Modification Of Mg-Zr-Nb System Microwave Dielectric Ceramics

With the vigorous development of microwave communication technology,portability,light weight,high reliability and low cost have gradually become the standard for next-generation communication equipment.MgZrNb₂O₈ ceramics with monoclinic wolframite structure have attracted the attention of many researchers due to their excellent dielectric properties.In this paper,we focus on the effects of ion-substituted and non-stoichiometry on the surface morphology,microstructure,and dielectric properties of ceramics.Dense Mg(Zr_1-xGe_x)Nb₂O₈ ceramics were synthesized.The relations between microstructure and microwave dielectric properties were studied.Experimentalε_r was found to be closely related to bond polarizability,and theoreticalε_r calculated based on P-V-L theory shows the same tendency with the experimental dielectric constant when the substitution amount of Ge⁴⁺changes.The increase in Q×f and|τ_f|were mainly attributed to the increase in packing fraction and the Nb-site bond valence,respectively.The Mg Zr(Nb_1-xSb_x)₂O₈ ceramics were synthesized through substituting Sb⁵⁺for Nb⁵⁺.Rietveld refinement was utilized to observe the impact of equivalent substitution on the microstructure of crystals.The phenomenon of non-monotonic changing in（Q×f）and monotonic increase inε_r was explained by bond ionicity and lattice energy based on the P-V-L theory.In addition,the deterioration ofτ_f was closely related to the reduction of bond energy.On the basis of the solid state reaction,the experimental procedure was optimized,and the high performance.Rietveld refinement and P-V-L theory were used as intrinsic factors of analyzing the changes in microwave dielectric properties.With the increase of(Sn_1/2W_1/2)⁵⁺substitution amount,ε_r of highly densified MgZrNb_2-x(Sn_1/2W_1/2)_xO₈ceramic decreased slowly,which was mainly ascribed to low bond iconicity.The optimal substitution of isovalent composite ions enhances the total lattice energy,leading to an increase in Q×f value.The increase ofτ_f was closely correlated with the decrease of the total bond energy.The intrinsic relationship between crystal structure,surface topography,P-V-L theory and dielectric properties of non-stoichiometric MgZrNb_2+xO_8+2.5x ceramics prepared were determined.The microwave properties as a function of the niobium ions content were found to be closely related to bond ionicity,lattice energy and bond energy calculated according to the P-V-L theory.