Ionic substitution effects on the structure-property relationship of Zn0.5Ti0.5NbO4 microwave dielectric ceramics

In the present study, ionic substitution strategies were adopted in ixiolite Zn0.5Ti0.5NbO4 ceramics, where the Co2+ and Ta5+ cations were used to partially replace the Zn and Nb sites and to investigate the structural evolution and microwave dielectric performances. It is interesting to find that the substitution of Co2+ and Ta5+ cations both lead to the reduction of volume of the unit cell, however, the variations of chemical bond behaviors are different, which is explained by the Rietveld refinement method, normalized bond analysis, polyhedral stretching behaviors, and the changes of characteristic Raman peaks. Furthermore, based on the complex chemical bond theory calculation, the drop of dielectric constant within the solid solution limits is attributed to the decline of average bond ionicity value along with the increase of ionic substitution content; while the lattice stability and uniformity of grain growth are mainly responsible for the variations of Q(f) value. After exceeding the solid solution limits, the developments of dielectric performances of Zn(0.5)Ti(0.5)NbO(4 )ceramics are more sensitive to the regulation of the secondary rutile phase. More importantly, the intrinsic dielectric properties analysis indicates that the absorption of structural phonon oscillation mainly causes the dielectric response in the microwave range.