Influences of substituting of(Ni_(1/3)Nb(2/3))for Ti^(4+)on the phase compositions,microstructures,and dielectric properties of Li_(2)Zn[Ti_(1-x)(Ni_(1/3)Nb_(2/3))_(x)]_(3)O_(8)(0<≤x≤0.3)microwave ceramics

Complex ion substitution is gaining more attention as an appealing method of modifying the structure and performance of microwave ceramics.In this work,Li_(2)Zn[Ti_(1-x)(Ni_(1/3)Nb_(2/3))_(x)]_(3)O_(8),0≤x≤0.3ceramics were designed based on the complex ion substitution strategy,following the substitution rule of radius and valence to investigate the relationship among phase compositions(containing oxygen vacancies and Ti^(3+)ions),microstructures,and microwave dielectric characteristics of the LZTNNx ceramics.The samples maintained a single Li_(2)ZnTi_(3)O_(8)solid solution phase as x≤0.2,whereas the sample of x=0.3 produced a second phase with the LiNbO_(3)structure.The appropriate amount of(Ni_(1/3)Nb_(2/3))^(4+)substitution could slightly improve the densification of the LZTNNx ceramics due to the formation of the LiZnTi_(3)O_(8)solid solution accompanied by a decrease in the average grain size.The presence of a new Aig Raman active band at about 848 cm^(-1)indicated that local symmetry changed,affecting atomic interactions of the LZTNNx ceramics.The variation of the relative dielectric constant(εr)was closely related to the molar volume ionic polarizability(α_(D)^(T)),and the temperature coefficient of the resonant frequency(τ_(f))was related to the bond valence(V_(1))of Ti.The increase in density,the absence of the Ti3+ions and oxygen vacancies,and the reduction in damping behavior were responsible for the decreased dielectric loss.The LZTNNO.2 ceramics sintered at 1120℃exhibited favorable microwave dielectric properties:εr=22.13,quality factor(Q×f)=97,350 GHz,andτ_(f)=-18.60 ppm/C,which might be a promising candidate for wireless communication applications in highly selective electronics.