Crystal structural characterization and microwave dielectric properties of Ca(Ta2-xNbx)O6 ceramics

The effects of Nb substitution Ta on crystal structures and the microwave dielectric properties of Ca(Ta2-xN-b(x))O-6 ceramics Were investigated(I ill this study. X-ray powder diffraction (XRPD) patterns of CTN ceramics with the I The composition x ranging from 0 to 1 show a single phase, which corresponds to,ill orthorhombic phase with an aeschynite-type structure (space group: Pnma), whereas those of the samples with compositions higher than x = 1.5 are indexable to an orthorhombic phase Willi a columbite-type structure (space group: Pbcn). Ill the composition range of 1.1-1.4, the two phases coexist in the CTN ceramics. As for the covalencies of CTN ceramics, those of the Ca-O and Ta/Nb-O) bonds strongly depend oil the crystal structure. In addition, the microwave dielectric properties of CTN ceramics significantly varied at compositions ranging from I to 1.5. depending oil the Weight fraction of the aeschunite and columbite phases. As it result. the microwave dielectric properties of CTN ceramics at x 1.5 showed it Q center dot f of 102,500GHz With a epsilon(x) of 16 and it tau(f) of -56ppm/degrees C. Moreover a near zero tau(r) value was obtained at x = 1.25 because of the coexistence of the aeschynite and columbite phases.