Study of relaxation in Li2Si2O5 by thermally stimulated depolarization current

Glass-ceramics containing mainly Li2Si2O5 and a small amount of Li3PO4 in crystalline phase was studied by integral and by partial thermally stimulated depolarization current (TSDC) in the temperature range 173–373 K. Partial measurements showed two single relaxation time peaks (P1 and P2) at 242 and 253 K, respectively, caused by the impurity–vacancy dipoles due to the presence of microcrystals and large interface area between the amorphous and the crystal phase. A comparative study was also carried out using samples with identical oxide contents but of a different microstructure. The results obtained with the glass showed a widely distributed relaxation process (P1′) with the maximum at 230 K caused by the short-distance motion of the alkali atoms and a higher temperature relaxation (P2′) caused by the relaxation of the interstitial charge. The background current caused by the thermally activated free charge was more expressed in glass than in glass-ceramics. The glass-ceramics systems showed a higher resistance to various motions than the amorphous ones.