Sintering behavior, phase structure and microwave dielectric properties of novel glass-free low-temperature cofiring NaCaLn(MoO4)3(Ln = Nd, Sm) ceramics.

Novel glass-free low-temperature cofiring NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics were prepared by a conventional solid-state reaction method, and their sintering characteristics, phase composition, micro-morphology and microwave dielectric properties were comprehensively investigated. The pure tetragonal scheelite structure of NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics were disclosed by the XRD patterns. The extremely dense micro-morphology was revealed in the SEM images, which corresponds to the density measurements results. Those results showed that the change of ε r values is closely related to relative density and molecular polarizability. The change in Q × ƒ value are considered influenced by both grain size and packing fraction. In addition, the largest contribution of Mo–O bonds to the Q × ƒ of NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics was revealed by P–V–L theory. The best dielectric properties were obtained at 850 °C and 875 °C for NaCaNd(MoO 4) 3 and NaCaSm(MoO 4) 3 , respectively: ε r = 11.06, Q × ƒ = 58,442 GHz, τ ƒ = −37.7 ppm/°C and ε r = 11.02, Q × ƒ = 47,190 GHz, τ ƒ = −43.8 ppm/°C. Furthermore, the good compatibility of these two ceramics with silver powder indicated that they have potential for LTCC applications. [ABSTRACT FROM AUTHOR]