Solid electrolytes with covalently bonded, interconnected polyhedral structures form another class of materials. These materials usually exhibit high Debye temperatures, thermal and chemical stability, and melting points, offering high operating temperatures for practical applications. Lithium Garnet type materials, with the general chemical formula A 3 B 2 (XO 4 ) 3 (A = Ca, Mg, Y, La or rare earth; B = Al, Fe, Ga, Ge, Mn, Ni or V; X = Si, Ge, Al), promise high thermal stability, high electrochemical window, as well as high ionic conductivity . They generally stabilize in the cubic phase with the space group Ia3d. The A, B, and X sites are respectively 8-fold (anti-prismatic), 6-fold (octahedral), and 4-fold (tetrahedral) coordinated to oxygen (Fig. ).