Microwave dielectric properties of ternary molybdate NaSrLn(MoO4)3 (Ln = Nd, Sm) ceramics for LTCC applications

Two kinds of scheelite-structure microwave dielectric ceramics with I41/a space group were prepared by the conventional solid-phase reaction method. The effects of different sintering temperatures on the crystal structure, lattice vibration and microwave dielectric properties of NaSrLn(MoO4)(3) (Ln = Nd, Sm) ceramics were investigated. XRD and Rietveld refinement results show that NaSrLn(MoO4)(3) (Ln = Nd, Sm) ceramics belong to tetragonal scheelite structure with I4(1)/a space group. The lattice vibration mode was analyzed by Raman spectroscopy, and the correlation between the dielectric performances and structure was established. The NaSrLn (MoO4)(3) (Ln = Nd, Sm) ceramics have high density (>97%) and excellent microwave dielectric properties of er = 10.47, Qf = 38951 GHz, Tf = -48.43 ppm/degrees C for NaSrNd(MoO4)(3) sintered at 775 degrees C and epsilon(r) = 9.55, Qf = 41081 GHz, tau(f) = -44.92 ppm/degrees C for NaSrSm(MoO4)(3) sintered at 800 degrees C. In addition, NaSrLn(MoO4)(3) (Ln = Nd, Sm) ceramics have excellent chemical compatibility with Ag electrodes, which means that the ceramic could be used in LTCC microwave devices.