Structural, Raman spectroscopic and microwave dielectric studies on spinel Li2Zn(1−x)NixTi3O8 compounds

Li2Zn(1−x)NixTi3O8 (x = 0, 0.1, 0.2, 0.4 and 1.0) microwave dielectric ceramics were studied with the help of powder X-ray diffraction and Raman spectroscopic measurements. These ceramic materials were synthesized by conventional solid state reaction method and observed to crystallize in cubic crystal system with P4332 space group. The cationʹs occupancies in tetrahedral and octahedral sites were quantified by performing Rietveld refinement. The occupancy of the Li1+ and Ni2+ in the respective tetrahedral and octahedral sites were found to increase, whereas occupancy of Zn2+ in tetrahedral site was observed to decrease with increase in Ni substitution. This decrease in occupancy of Zn2+ in tetrahedral site increased the AC conductivity by allowing the migration path 8c-12d-8c, which in turn increases the dielectric loss in these compounds. Dielectric constant and observed ionic polarizability were linearly decreased by increasing the Ni substitution. Raman spectra revealed that the shift in A1g mode of ZnO4 tetrahedra to higher wavenumber side was due to increase of Li1+ at tetrahedral site and narrower FWHM of symmetric stretching mode of Zn–O corresponded to the higher quality factor.