Preparation and Ionic Conductivity of Al-Doped Mg0.5Ti2(PO4)3

Al-doped Mg0.5(1+x)AlxTi2-x(PO4)(3) has been prepared by a sol-gel method and the conductivity has been evaluated by an ac impedance method to determine the optimum lattice volume for Mg-ion conduction. Instead of using Ti in the samples, 10-15 mol%Al was used, resulting in lattice contraction in the c-axis direction. The samples, sintered at 500-80 degrees 0C for 12 h by a reaction sintering method, had a relative density of 70-80% and their grain size was 2-3 mu m. The ionic conductivity calculated from the grain and grain boundary resistance at 600 degrees C was 7.1 x 10(-5) and 1.3 x 10(-5) S/cm, respectively. The activation energy of the grain conductivity was 128 kJ/mol in the temperature range of 300 to 600 degrees C. By comparing ionic conductivity of various-doped titanium phosphates, optimum lattice volume was estimated to be 1.304 nm(3). [doi:10.2320/matertrans.MBW201111]