Effects of Zn2+ substitution on the crystal structure, Raman spectra, bond energy and microwave dielectric properties of Li2MgTiO4 ceramics

The rock salt structured Li2Mg1-xZnxTiO4 ceramics were prepared by the conventional solid-state method. X-ray diffraction, bond energy and Raman spectra were employed to investigate the crystal structure and polarization characteristics of the ceramics. With the x value increasing from 0 to 0.5, the dielectric constant of Li2Mg1-xZnxTiO4 gradually increased from 15.36 to 18.42, which was attributed to the higher polarizability of zinc ions. The variation trend of the polarizability was also in accordance with that of Raman vibration modes. The quality factor of specimens initially increased and then significantly decreased with the increase in Zn2+ substitution, which could be explained in the variation of packing fraction. In addition, the temperature coefficient of resonant frequency showed a tendency of decrease with the decreasing bond energy, implying that the substitution of Zn2+ influenced the crystal stability of Li2MgTiO4. An appropriate amount of zinc substitution effectively improved the dielectric permittivity and decreased the dielectric losses of the matrix. The Li2Mg0.9Zn0.1TiO4 ceramics sintered at 1350 degrees C possessed excellent microwave dielectric properties with epsilon(r) = 16.20, Q center dot f = 145,200 GHz and tau(f) = -4.03 ppm/degrees C, which made these ceramics promising for future applications. (C) 2017 Elsevier B.V. All rights reserved.