Crystal structure, lattice energy and microwave dielectric properties of melilite-type Ba_1-xSrxCu₂Ge₂O₇ ceramics

The Ba(1-x)SrxCu(2)Ge(2)O(7) was successfully obtained through the solid-state reaction method, with single -phase BaCu2Ge2O7 formed at 850 degrees C. Scanning electron microscopy analysis revealed the excellent chemical compatibility of Ba(1-x)SrxCu(2)Ge(2)O(7) with silver. The properties of Ba(1-x)SrxCu(2)Ge(2)O(7) ceramics were explained using the P -V -L theory. The e(r-corr )decreased with the polarization rate (Sigma N-u*(chi)b(u)) and ion polarization of the unit cell. The Qxf increased with the chemical bond strength and lattice energy (Ucal), particularly the lattice energy of the Ge -O bond (U(Ge-O)). The af exhibited an opposite trend to the Qxf value and was influenced by the U(CuO) and susceptibility of the Cu -O bond (chi(Cu-O)). Sintering at 875( degrees)C for 3 h yielded optimal microwave dielectric performance for Ba1-xSrxCu2Ge2O7 ceramics, with observed values of epsilon(r) = 9.26 +/- 0.14, Qxf = 85,660 +/- 4200 GHz, and tau(f )= -15.6 +/- 1.1 ppm/C-degrees at x = 0.10. These promising microwave dielectric properties make Ba(1-x)SrxCu(2)Ge(2)O(7) a potential candidate for LTCC material applications.