Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is one promising solid electrolyte material for lithium batteries. Obtaining the desired high conductivity requires high density and formation of the cubic phase. Small amount of tantalum has been shown to stabilize the cubic crystal structure and increase the conductivity. In this work, LiOH additives were introduced into the cubic LLZO at the final sintering step of the co-precipitation method to densify LLZO. Results on the synthesis, material characterization, and electrochemical impedance spectroscopy of dense tantalum-doped LLZO are presented.