Bond characteristics, microstructure, and microwave dielectric properties of Bi2O3–ZnO–B2O3 glass-ceramics with Li2O substitution

The effect of Li2O substitution on the sintering behavior, lattice structure, microstructure, and microwave dielectric properties of ZnO–B2O3–Bi2O3 glass-ceramics was studied by various amounts of Li2O to substitute ZnO. The substitution of Li2O decreases the glass network connectivity and thus decreases the sintering temperature of the glass. In the sintered glass-ceramics, the substitution of 0.2 mol% Li2O leads to the most significant lattice activation resulting in the glass-ceramic exhibiting the smallest cell volume of Zn3B2O6 crystal and the microstructure with fine and uniform grains. The P–V-L theory is innovatively applied to glass-ceramic materials to characterize the variation in bond characteristics caused by lattice activation and it indicates that the 0.2 mol% Li2O substitution decreases the Zn–O bond ionicity and increases the lattice energy of the B–O bond, in the Zn3B2O6 crystalline phase. The refinement of microstructure and the optimization of bond characteristics improve the microwave dielectric properties of glass-ceramics. The glass-ceramic with 0.2 mol% Li2O substitution sintered at 620 °C for 5 h exhibits excellent microwave dielectric properties of εr ∼5.05, Q×f ∼15,383 GHz, τf ∼ −6 ppm/°C and good chemical compatibility with Ag or Al electrodes, which is a favorable candidate for application in ULTCC substrate materials.