In this paper, the Li 2/3(1Àx) Sn 1/3(1Àx) Mg x O (LSMxO) ceramic systems were prepared by solid-state reaction using novel atmosphere-controlled sintering (x = 0-4/ 7). Pure Li 2 SnO 3 was observed for x = 0, the Li 2 Mg 3 SnO 6 and Li 2 SnO 3 coexisted for x = 1/7, and the coexistence of three kinds of phases was detected for x = 1/5 and 1/4, including Li 4 MgSn 2 O 7 impurity phase. Pure Li 2 Mg 3 SnO 6 -like phase with cubic rock salt structure in Fm-3m space group was obtained in the range of 1/3-4/7. All samples showed well-dense and smooth microstructures. The microwave dielectric properties highly depended on the phase composition, bond valence, FWHM of Raman spectrum, Raman shift, average grain sizes, and octahedral dis-
| INTRODUCTIONMicrowave dielectric ceramics have played a paramount role as key components in the microwave devices ranging from any hand-held terminals to base stations due to the rapid growth in wireless communication industry.1 To meet the specific request of fifth-generation (5G) communication and applications, these ceramic systems are required to possess the adjustable dielectric constant (e r ), high quality factor (Q 9 f) and near-zero temperature coefficient of the resonant frequency (s f ). [2][3][4] Great efforts have been made to explore the new ceramic systems, and study the correlation between structure and microwave dielectric characteristics.In the past half-century, Li 2 BO 3 -MgO system (B = Ti, Sn), which is affiliated to the big family of rock salt structure phases, has drawn some attentions due to the phenomenon of order-disorder phase transition. In the case of Li 2 TiO 3 -MgO system, the substitution mechanism between Li/Ti and Mg has been confirmed by numerous literatures, [5][6][7][8][9][10][11][12][13] which could be expressed as 2Li. The substitution of Li/Ti for Mg leads to the ordered superstructure of Li 2 TiO 3 phase transforming from a monoclinic structure in C2/c space group to a disordered cubic structure in Fm-3m space group. Two phase systems, Li 2 TiO 3 (0 ≤ x < 1/5) and Li 2 Mg 3 TiO 6 (1/ 5 ≤ x ≤ 1/2) phase, were found according to the formula