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 °C, such that τf remains a constant value of ∼12.4 ppm/°C. Accompanied by the appearance of impurity phases (Li2SnO3)ss and especially (MgO)ss at higher sintering temperatures, excellent microwave dielectric properties of εr = 13.1-13.5, Q × f = 106,800-126,810 GHz and τf  = 0-−4.2 ppm/°C are obtained in samples sintered at 1215-1260 °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 εr∼13.7, Qxf∼97,000 GHz (x ≤ 3) and τf ∼8-13 ppm/°C sintered at 850 °C for potential LTCC applications, and εr ∼13.9, Qxf∼146,000 GHz and τf ∼1.5-6 ppm/°C (x ≥ 4) as sintered 1000 °C, exhibiting large potentials for microwave dielectric candidates.