Unveiling Na-substitution effects on charge transport in Pr0.8K0.2−xNaxMnO3 using experimental analysis and kernel density estimation

Abstract

The present work reports on the effects of substituting potassium with monovalent sodium on the electrical properties of Pr_0.8K_0.2−xNa_xMnO₃ (x = 0.00, 0.05, 0.1, 0.15 and 0.2) manganites. The electrical measurements indicate that Pr_0.8K_0.2MnO₃ exhibits a metal–semiconductor transition at T_M–S. The temperature dependence of the electrical conductivity indicates that introducing low Na concentrations (x < 0.15) does not affect the material's behavior. Beyond a sodium concentration limit (x = 0.15), the studied compounds exhibit semiconductor behavior over the studied temperature range. In this case, it is found that introducing high Na concentrations blocks the cation–cation interactions and reinforces the cation–anion–cation states at low temperatures. In the same context, it is observed that the increase in the Na content reduces the conductivity of the manganites over the whole investigated temperature range. At elevated temperatures and beyond T_sat, all the elaborated manganites are characterized by the occurrence of conductivity saturation. For x < 0.15, the samples exhibit both cation–cation and cation–anion–cation interactions at low and high temperatures, respectively. For x = 0.15 and 0.20, the manganites exhibit cation–anion–cation interactions over a large temperature domain between 80 K and T_sat. However, the x = 0.15 and 0.2 samples are characterized only by the cation–anion–cation interactions. Consequently, the critical temperature for x = 0.00, 0.05 and 0.1 samples represents a direct switching point from semiconductor to metallic behavior. At high frequencies, the hopping energy is predicted to decrease with increasing frequency, which can be linked to the change in the polaron radius. For all the studied samples, kernel density estimation (KDE) is proposed as an effective method to gain information on the probability density function associated with the random variable. The KDE-based method may be used to identify the origin of the observed marginal distributions at low and high temperatures for all the studied ceramics. The observed dual electrical–microstructural functionality establishes Pr_0.8K_0.2−xNa_xMnO₃ (x = 0.00, 0.05, 0.1, 0.15 and 0.2) as a promising manganite for advanced switching applications in next-generation electronic systems.