A new Li-based ceramic of Li4MgSn2O7: Synthesis, phase evolution and microwave dielectric properties

A pure-phase Li4MgSn2O7 (L4MS) was successfully synthesized through optimizing the calcination condition. Microwave dielectric properties of the L4MS ceramic with the phase evolution were investigated together with its low-temperature sintering. The sample maintains a single L4MS phase as sintered below 1200 degrees C, such that tau(f) remains a constant value of similar to 12.4 ppm/degrees C. Accompanied by the appearance of impurity phases (Li2SnO3)(ss) and especially (MgO)(ss) at higher sintering temperatures, excellent microwave dielectric properties of epsilon(r) = 13.1-13.5, Q x f = 106,800-126,810 GHz and tau(f) = 0-- 4.2 ppm/degrees C are obtained in samples sintered at 1215-1260 degrees C for 4 h. Reduction of sintering temperature using LiF sintering aid also helps achieve pure-phase dense L4MS ceramic. The L4MS + x wt.% LiF ceramic exhibits epsilon(r) similar to 13.7, Qxf similar to 97,000 GHz (x <= 3) and tau(f) similar to 8-13 ppm/degrees C sintered at 850 degrees C for potential LTCC applications, and epsilon(r) similar to 13.9, Qxf similar to 146,000 GHz and tau(f) similar to 1.5-6 ppm/C (x >= 4) as sintered 1000 degrees C, exhibiting large potentials for microwave dielectric candidates.