Observation of lithium colloid melting in irradiated Li2O

When irradiated with energetic electrons near room temperature Li2O Single crystals exhibit metallic Li colloids, as shown by ESR (electron spin resonance) and Li-7-NMR experiments. These colloids were established as being of two types of very different sizes. ESR experiments performed above room temperature, in the range up to 300 degrees C show melting of the metallic colloids as observed on the line parameters, affecting simultaneously the width and the intensity of the ESR signal. The phenomenon is complicated by the fact that annealing effects of the metallic colloids are superimposed on the purely thermal behaviour. We performed also DSC (differential scanning calorimetry) experiments which are manifesting directly the reversible melting of the colloids; from the integrated intensity of the DSC peaks, we could deduce the lithium metal concentration, which is in good agreement with the value obtained from the ESR signal intensity.