Synthesis, thermal and electrical properties of Li 1+ δMn 2− δO 4 prepared by a sol–gel method

Abstract

The Li 1+ δ Mn 2− δ O 4 samples (0.00≤ δ≤0.20) were obtained by a sol–gel method and characterized using: chemical analyses, XRD, SEM, TGA, DSC, electric conductivity and thermoelectric power. The obtained results were discussed in relation to the calcination temperature, and to the results obtained on commercial LiMn 2O 4. The samples calcined at 300 °C (S-samples) consisting small excess of Li ( δ≤0.04) showed no phase transition at 285 K and no disturbance in electric conductivity and thermoelectric power, as observed for the related samples calcined at 800 °C (H-samples). Partial thermal decomposition of the S-samples or oxygen uptake by the H-samples were observed during TGA experiments above 350 °C. The beginning of the thermal decomposition of the H-samples started at higher temperatures, depending on Li-contents. At about 920 °C, the rapid acceleration took place independently on type of the samples. The thermal decomposition up to 800 °C seems to be reversible, owing to the samples reoxidation.