Polycrystalline sample of Ba4LiNb3O12 is synthesized in the temperature range of 1150 degrees-1180 degrees C by the conventional solid-state reaction method. A phase transition from cubic to hexagonal perovskite is observed around 1160 degrees C. It is noted that hexagonal phase of Ba4LiNb3O12 obtained at 1180 degrees C could be stabilized at a considerably lower temperature (similar to 950 degrees C) with BaCu(B2O5) (BCB) added. BCB addition effectively improves the densification of Ba4LiNb3O12 ceramic and significantly affects the microwave dielectric properties. When 4 wt% BCB is added, a dense ceramic can be sintered at 950 degrees C with a epsilon(r) of 34.5, a high Q x f of 29 600 GHz, and a low tau(f) of 12.4 ppm/degrees C. Moreover, BCB-added Ba4LiNb3O12 ceramics have a chemical compatibility with silver.