Enhanced quality factor and low-temperature densification of BaCu2-xMgxSi2O7 ceramics with MBSCA glass

Mg 2+ substitution suppresses Jahn-Teller distortion of the [Cu/MgO 4 ] unit. • P-V-L lattice energy trends serve as a qualitative descriptor of Q × f variation. • Dense sintering at 925 °C and compatibility with Ag meet LTCC requirements. • Optimum properties: ε r = 8.01, Q × f = 49,558 GHz, and τ f = −30.6 ppm/°C. BaCu 2 Si 2 O 7 is a promising low-permittivity microwave dielectric ceramic; however, its high sintering temperature (>1000 °C) limits c°mpatibility with the low-temperature co-fired ceramics (LTCC) process. Herein, Mg 2+ was partially substituted for Cu 2+ in BaCu 2- x Mg x Si 2 O 7 ( x = 0–0.20) ceramics, with 2 wt% MBSCA glass. All compositions were densified at 925 °C. The average bond-length difference Δ d of the four-coordinate [Cu/MgO 4 ] unit decreases with Mg substitution up to x  = 0.10, indicating suppressed local structural distortion, before a slight rebound at higher x . The measured Q × f and Δ d exhibit consistent composition-dependent trends, both reaching their optimum at x  = 0.10, where reduced structural distortion and improved densification jointly contribute to the enhanced Q × f . The optimized composition achieves (measured at 14.74 GHz) ε r = 8.01, Q × f = 49,558 GHz, and τ f = –30.6 ppm/°C, along with excellent chemical compatibility with silver electrodes; although |τ f | increases with Mg content, it remains moderate at the optimum. These results demonstrate that BaCu 2- x Mg x Si 2 O 7 + 2 wt% MBSCA ceramics are promising candidates for LTCC applications.