Microwave dielectric properties of glass free low temperature co-fired LixNa1−xY(MoO4)2(x = 0–0.4) ceramics with temperature stability

Abstract

This study set out to the microwave dielectric properties of novel low temperature co-fired LixNa1−xY(MoO4)2(x = 0–0.4) ceramics and adjusted their temperature stability by doping Li+. The XRD confirmed that the doping in the range of x = 0–0.4 would not cause the emergence of the second phase, and the doped Li+ completely entered the lattice and formed LixNa1−xY(MoO4)2 solid solution ceramics, which had tetragonal scheelite structure. The εr and τƒ of LixNa1−xY(MoO4)2 ceramics move in a positive direction with the increase of doping amount, while the downward trend is observed in Q × ƒ. On the one hand, the change of εr and Q × ƒ at different sintering temperatures strongly depends on extrinsic factors such as density, grain size, and holes. On the other hand, this change is closely related to the ionicity, lattice energy, and packing fraction at different compositions. Besides, the change of τƒ can be attributed to the influence of bond valence. When x = 0, NaY(MoO4)2 ceramics have the highest Q × ƒ, and when x = 0.25, Li0.25Na0.75Y(MoO4)2 ceramics have the best temperature stability. Their properties are εr= 10.69, Q × ƒ= 53080.73 GHz, and τƒ= −46.84 ppm/°C and εr= 12.18, Q × ƒ= 30373.95 GHz, and τƒ= −6.35 ppm/°C, respectively. Normally, there is good compatibility between Li0.25Na0.75Y(MoO4)2 ceramics and Ag powders.