Effect of VO43−Substitution for PO43−on Electrical Conductivity in the Nasicon Li3Sc2(PO4)3Compound

In this work, VO43− substitution for PO43− in the Nasicon structured Li3Sc2(PO4)3 was used to enhance its ionic conductivity. The VO43− substitution resulted in a homogeneous compound Li3Sc2(PO4)3-x(VO4)x within a wide composition range of 0 ≤ x ≤ 1.2; further increase in x led to precipitation of the crystalline phases VPO5, V(PO3)3 and ScVO4. Electrical conductivity of the VO43−-substituted samples increased with the VO43− content, and the sample with x=1.5 exhibited the highest conductivity (8.41×10−3 S m−1) at room temperature and the lowest activation energy (39.65 kJ mol−1). The obtained conductivity was two orders of magnitude higher than that of the non-substituted sample and nine times higher than those of the Zr4+ and SiO44−-substituted compounds. The present study demonstrates that the VO43− anion substitution for PO43− is a promising technique to improve ionic conductivity of the Nasicon compound.