Microstructure and dielectric properties of low-temperature sintered MgO-based ceramics at millimeter wave and terahertz frequencies

Low-temperature co-fired ceramics (LTCC) applied in millimeter/microwave and terahertz frequencies (5G/6G) have attracted a lot of attention recently. In this study, MgO-based dielectric ceramics were successfully sintered at 950(degrees)C with the sintering aids: x wt.% of LiF fluoride (x=2, 4, 6, 8, 10) and 0.5wt.% of BBSZ (Bi2O3-B2O3-SiO2-ZnO) glass. BBSZ glass was introduced as another sintering aid to facilitate the sintering and densification. Crystalline structure and micro-morphology were investigated and analyzed. Dielectric properties (epsilon(r), Q x f, tau(f)) at millimeter/microwave and terahertz wave frequencies were also studied. The ionic characteristics of Mg-O bond (f(i)), the lattice energy (U) and the bond energy (E) were calculated and analyzed. It is suggested that the optimal x = 4, where epsilon(r )= 10.5, Q x f = 120,000GHz (@12GHz) and tau(f )= -26ppm/C-degrees at millimeter/microwave range. When the frequency was up to terahertz (1.0THz), the epsilon(r) values were 8.8-9.35 and the tan delta were 5.6 x 10(-3)-8.7x10(-3). The experimental results indicated that the low-temperature sintered MgO-based ceramics have potential for millimeter/microwave and terahertz communication applications.