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 (P-1 and P-2) 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 (P-1') with the maximum at 230 K caused by the short-distance motion of the alkali atoms and a higher temperature relaxation (P-2') 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. (C) 2002 Elsevier Science B.V. All rights reserved.