Effects of the intercalation time on the dielectric properties of Na2xMn1?xPS3

Manganese thiophosphate powders have been intercalated with sodium ions at two different intercalation times (150 min and 180 min) in order to evaluate the influence of this parameter on the dielectric properties of the obtained compounds labeled like Na_2xMn_1?xPS₃. In particular, dielectric permittivity measures have been carried out as a function of temperature (80 K–350 K) and frequency (20 Hz to 1 MHz) and compared with each other and with those of the pure matrix and of the Na_2xMn_1?xPS₃ compound corresponding to a 120 min intercalation time. Both investigated compounds show a dielectric response characterized by a loss peak at low temperatures, by a strong dispersion at low frequency and at not very high temperatures and by a crossover frequency showing an Arrhenius temperature dependence in agreement with what already observed in Na_2xMn_1?xPS₃ (120 min). The results have been also discussed in terms of ac conductivity, Maxwell–Wagner–Sillar (MWS) polarization, electrode polarization and dc conductivity and all the above cited features have been attributed to the Na⁺ ions which are, by their nature, hopping charge carriers that behave like jumping dipoles in their alternate motions and simultaneously show conducting characteristics resulting from their extended hopping over many sites. This attribution allows us to classify the analyzed sodium compounds like hopping charge carrier systems in which a greater Na intercalation time translates into a decrease in the loss peak intensity and an increase in the activation energy associated to the crossover frequency.