STUDY OF POLY(METHYL METHACRYLATE) SPACE-CHARGE RELAXATION BY TSDC

A windowing polarization technique has been applied to form PMMA therm oelectrets. The stimulated depolarization currents of these electrets in the range of polarization temperatures between 380 and 405 K show o nly a rho peak which is attributed to space charge relaxation. The are a of this peak exhibits a maximum at a certain polarization temperatur e (the optimal polarization temperature). The results obtained by fitt ing the depolarization currents to the general kinetic order model are consistent with the existence of a space charge polarization mechanis m with a distribution of trapping depths, which can be qualitatively d escribed. Moreover, the Arrhenius-like kinetic parameters deduced from the relaxation times can be interpreted in terms of a compensation la w. Finally, the optimal polarization in PMMA can be described by means of a distribution of trapping levels. (C) 1997 Elsevier Science Ltd.