Synthesis and ionic conductivity of pure and Co-doped lithium barium diphosphates Li2 − 2xCoxBaP2O7 (0 ≤ x ≤ 0.06)

Polycrystalline Li2BaP2O7 was obtained by heating a stoichiometric mixture of Li2CO3, BaCO3 and NH4H2PO4 at 750 °C for 12 hours in an air atmosphere. Co-doped samples Li2 − 2xCoxBaP2O7 (0.02 ≤ x ≤ 0.06) were prepared in the same way by adding predetermined amounts of cobalt(II) acetate tetrahydrate Co(CH3COO)2·4H2O in the reaction mixture. The identity of the compounds was confirmed by elemental and X-ray diffraction analysis. The ionic conductivity, ascribed to the Li+ ion motion, was analysed by impedance measurements (frequency range: 1–105 Hz, temperature range: 150–600 °C) on polycrystalline pellets sintered at 720 °C for 12 hours. The ionic conductivity is discussed on the basis of the structural characteristics of the samples.