A Li1.4Al0.4Ti1.6(PO4)(3) gel was successfully prepared by a citrate process and converted into nanostructured and highly Li+-conductive Li1.4Al0.4Ti1.6(PO4)(3) glass-ceramics through heat treatment at 700-900 degrees C. The experimental results indicated that the Li-ion conductivity of the glass-ceramics depended greatly on the grain size of the conducting phase in the specimens. An excellent room-temperature conductivity as high as 1.36 x 10(-3) S cm(-1) was obtained, which is one of the highest lithium-ion conductivity for solid electrolytes.