A structural investigation of the influence of dopants on the electronic properties of LiCoVO4

The influence of 6% Co substitution in LiCoVO4 for Fe, Cr and Cu was investigated to determine the influence on the structural and electronic properties of the substituted inverse spinel. It was found that the lattice parameter of the inverse spinel structure changed and that no second phases were found. The oxidation state of the different ions were determined by XPS and it was found that for both the Fe3+ and Cr3+ substitution the oxidation state of the Co2+ did not change. The XPS results showed that the oxidation state of vanadium was 5+ and is the only cation that partly changed to an oxidation state of 4+, for charge compensation. This change in the oxidation state led to an increase in the electrical conductivity by a factor of 10. The Cu2+ substitution also led to an increase in the electrical conductivity but smaller. Rietveld refinement analyses of the inverse spinel led to the conclusion that no large reorientation occurred for the different cations at the different sites.