Nanocrystalline powders of La 10−x Ge 5.5 Al 0.5 O 26±δ (x=0–0.5) with an average crystallite size of 50nm were prepared by a freeze-drying precursor method. These powders were used to obtain dense ceramic materials at rather low temperature as 1100–1200°C for 1h and to study the transport properties by impedance spectroscopy. The composition with the highest La-content (x=0) exhibits a second-order phase transition from triclinic (P1¯) to hexagonal (P6 3 /m) space groups around 750°C, whereas for x≥0.2 the materials presents hexagonal structure in the whole temperature range studied. The thermal properties of these materials were investigated by high temperature X-ray diffraction (XRD), thermal analysis (TG/DTA) and impedance spectroscopy. These results confirmed the incorporation of water in the germanate-apatite structure. However, the conductivity resulted to be independent on the gas atmosphere used, which seems to indicate that the proton contribution to the overall conductivity is negligible in these materials.