Effects of BaCu(B2O5) additives on the crystal structures and dielectric properties of CaMgGeO4 ceramics for LTCC applications

Abstract

A CaMgGeO₄ (CMG) ceramic with an olivine structure was fabricated by the traditional solid-phase reaction method; this material was dense at 1300 °C/6 h and exhibited excellent dielectric properties (ε_r = 6.83, Q × f = 125 432, f = 14.9 GHz). The effects of BaCu(B₂O₅) (BCB) on the sintering characteristics, crystal structures and microwave dielectric properties of CMG systems were studied. BCB can effectively reduce the sintering temperature (T_s) of the CMG ceramic, and when the amount of BCB is 16 wt%, the T_s can be lowered to 875 °C. The CMG ceramic containing 8 wt% BCB shows excellent dielectric properties (ε_r = 7.01, Q × f = 73 962, f = 14.8 GHz) at 940 °C/6 h. Raman mode 11 moves to a lower wavenumber with increasing BCB content, while the BCB content has the opposite effect on the dielectric constant; however, the full width at half-maximum (FWHM) value of mode 11 correlates negatively with the Q × f values. In addition, the change in the packing fraction is similar to that in the Q × f values with increasing BCB content. A decrease in the packing fraction means an increase in the vibrational space and possibly non-resonance, which in turn reduces the Q × f value. In addition, the ceramic has good chemical compatibility with the Ag electrode, indicating broad application prospects in low-temperature co-fired ceramics (LTCCs) for CMG.