Microwave Dielectric Properties of Na5RE(MoO4)4 (RE = La, Gd, Dy, Er) Ceramics with a Low Sintering Temperature.

Na₅RE(MoO₄)₄ (RE = La, Gd, Dy, Er) ceramics have been synthesized by the conventional solid-state reaction method. The crystallizations, microstructures and microwave dielectric properties of Na₅RE(MoO₄)₄ ceramics were also investigated. The room-temperature x-ray diffraction patterns of Na₅RE (MoO₄)₄ ceramics illustrate a tetragonal structure with a I 4₁/a space group. The grain size of Na₅La(MoO₄)₄ is larger than that of Na₅RE(MoO₄)₄ (RE = Gd, Dy, Er) ceramics, and uneven grains are observed in the systems. Na₅RE (MoO₄)₄ ceramics sintered at 570-690°C for 4 h possess excellent microwave dielectric properties with ε_r = 6.4-8.4, τ_f = − 27.7-34.3 ppm/°C, and Q × f = 4073-24411 GHz at their optimum sintering temperature. The nonreactivity of Na₅Er(MoO₄)₄ with silver is evidenced by x-ray diffraction, and SEM and EDS analysis reveal that silver can be a co-firable electrode material for the present ceramics. [ABSTRACT FROM AUTHOR]