An In-depth Analysis of Dielectric and Electrical Conduction Mechanisms in Magnesium-Substituted LiTaO3 Solid Solutions

Abstract

In this work, Li_1–xMg_x/2Ѷ_x/2TaO₃ ceramic materials have been prepared for 0.00 ≤ x ≤ 0.10, where Ѷ is a vacancies site. The X-ray diffraction analysis indicated the formation of a pure phase, with no evidence of secondary phases detected. These findings confirm that all samples have crystallized into a singular pure phase, exhibiting the characteristic structural arrangement associated with the R₃C space group. The surface texture analysis of the prepared material showed a uniform distribution of grains with minimal voids, indicating high sample density. Additionally, substituting magnesium (Mg) led to a decrease in grain size, highlighting the impact of magnesium substitution on grain refinement. Ac impedance measurements were made between the temperatures of 640 and 800°C and the frequency range of 1 kHz to 2 MHz. The effect of magnesium doping Low frequency relaxation is attributed to space charges, while high frequency relaxation is attributed to ferroelectric dipoles. The electrical properties, which vary with frequency, were examined using complex impedance spectroscopy. Different types of investigations, including Nyquist plots, the real and imaginary components of impedance, conductivity, module formalism, and activation energy of charge carriers, were applied to clarify the connections between microstructure and electrical properties. The dielectric constant is high at low frequencies and decreases at moderate frequencies, indicating the Maxwell–Wagner contribution to the dielectric response. Systematic adjustments have been made with the aid of the Cole–Cole model. It appears for the identified relaxations that at temperatures close to T_C, the pass through is at its maximum and the relaxation time is thermally stable. A temperature-dependent, non-Debye relaxation process is revealed by impedance spectroscopic studies. Conductivity spectra revealed the presence of a jump mechanism in the electrical transport process. Activation energies between 1.12 and 1.39 eV indicate that the conduction of lithium vacancies takes place via a jump mechanism.