Synthesis and ionic conductivity of Na1+2xMxZr2-x(PO4)3 (M – Mg, Mn) NASICON-type ceramic materials

Ceramics of the Na_1+2xM_xZr_2-x(PO₄)₃ (M − Mg, Mn) composition were synthesized by the co-precipitation technique with subsequent annealing. The samples were characterized using X-ray diffraction with the Rietveld refinement, scanning electron microscopy, and impedance spectroscopy. The studied phosphates belong to the NASICON type structure. The solid solutions (0 ≤ x ≤ 1.0) were shown to be formed in the investigated systems. To study the effect of the chemical composition and sintering additive on conductivity, two series of ceramics were prepared for each phosphate: with and without ZnO (2 wt%) additive. The ionic conductivity of the studied phosphates followed the Arrhenius law and passed through a maximum with x growth. It was shown that the addition of zinc oxide also leads to partial substitution of zirconium in the lattice and an increase in ionic conductivity. The highest conductivity was achieved for the Na_2.6Mg_0.8Zr_1.2(PO₄)₃ ceramic with 2 wt% ZnO additive (6.8∙10⁻³ S cm⁻¹ at 673 К).