Synthesis and ionic conductivity of NASICON-type Li1.4Al0.4Ti1.6(PO4)3 fine powder by a novel multi-step glass crystallization method

Li _1.4Al _0.4Ti _1.6(PO ₄) ₃ (LATP) with a Na super ionic conductor (NASICON)-structure was successfully synthesized by a novel glass-crystallization method. First, glass specimens were prepared by heating raw materials LiPO ₃, Li ₂CO ₃, Al(PO ₃) ₃, and TiO ₂ at 1300 °C for 1 h in air, and then a two-step heat treatment was performed on the glass specimens to synthesize the LATP. Li ₂Ti ₂(PO ₄) ₃ particles formed in the glass specimen during the first heat treatment at 460°C for 2 h, followed by a change of Li ₂Ti ₂(PO ₄) ₃ to LATP during the second heat treatment at 720°C for 20 h. The resultant fine LATP powder had a sharp particle-size distribution with a 50% integrated diameter of 1.9 μm. The ionic conductivity of the LATP-sintered body that was fabricated at 1000 °C by using the LATP fine powder was 1.34 × 10 ⁻⁵ S cm ⁻¹ at 25 °C, which was superior to that obtained by a conventional method.