High‐Q microwave ceramics of Li₂TiO₃ co‐doped with magnesium and niobium

Abstract

In order to solve the problems of acceptor/donor individual doping in Li2TiO3 system and clarify the superiority mechanism of co‐doping for improving the Q value, Mg + Nb co‐doped Li2TiO3 have been designed and sintered at a medium temperature of 1260°C. The effects of each Mg/Nb ion on structure, morphology, grain‐boundary resistance and microwave dielectric properties are investigated. The substitution of (Mg1/3Nb2/3)4+ inhibits not only the diffusion of Li+ and reduction in Ti4+, but also the formation of microcracks in ceramics, which promotes the enhancement of Q value. The experiments reveal that Q × f value of Li2TiO3 ceramics co‐doped with magnesium and niobium is 113 774 GHz (at 8.573 GHz), which is increased by 113% compared with the pure Li2TiO3 ceramics. And the co‐doped ceramics have an appropriate dielectric constant of 19.01 and a near‐zero resonance frequency temperature coefficient of 13.38 ppm/°C. These results offer a scientific basis for co‐doping in Li2TiO3 system, and the outstanding performance of (Mg + Nb) co‐doped ceramics provides a solid foundation for widespread applications of microwave substrates, resonators, filters and patch antennas in modern wireless communication equipments.

A novel microwave dielectric ceramic Li2NiZrO4 with rock salt structure

“…When the sintering temperature kept rising, the abnormal grain growth and second phase precipitation led to the decline of Q f value. 32 The trend of s f with the sintering temperature is also shown in Fig. 5.…”

Characterization of cation disorder and oxygen vacancies in Li‐rich Li2TiO3

“…The reduction in the (0 0 2) peak intensity indicates that the degree of cation disorder is increased, which may be caused by the substitution of lithium for titanium, as that of Mg/Nb/Cu/etc. doped Li 2 TiO 3 23–26 …”

“…doped Li 2 TiO 3 . [23][24][25][26] The Rietveld refinement plots and lattice parameters of the L2.0 and L2.2 samples sintered in air are shown in Figure 4. As can be seen, the calculated value and the experimental pattern were well fitted.…”

Temperature Stability of Li2TiO3‐Zn2SiO4 Microwave Dielectric Ceramics

“…Nonetheless, the glass‐derived compounds such as B 2 O 3 which have lower ϵ r value and higher dielectric loss significantly hindered the improvement of microwave dielectric properties. Furthermore, Li 2 TiO 3 ceramics doped with BaCu(B 2 O 5 ), H 3 BO 3 , LiF, Mg/Nb, Li 2 O‐ZnO‐B 2 O 3 and Li 2 WO 4 have been successfully prepared and proved to optimize the microwave dielectric properties of Li 2 TiO 3 ceramics [14–19] . (2) Formation of solid solutions.…”

“…Furthermore, Li 2 TiO 3 ceramics doped with BaCu(B 2 O 5 ), H 3 BO 3 , LiF, Mg/Nb, Li 2 O-ZnO-B 2 O 3 and Li 2 WO 4 have been successfully prepared and proved to optimize the microwave dielectric properties of Li 2 TiO 3 ceramics. [14][15][16][17][18][19] (2) Formation of solid solutions. Li 2 Ti 1 À…”