Comprehensive analysis of Rb2Mg2(WO4)3: structural, morphological, dielectric, and CBH model-based charge transport for optoelectronic applications

Abstract

In this study, a novel Rb₂Mg₂(WO₄)₃ triple tungstate was successfully synthesized via a conventional solid-state reaction and comprehensively characterized for its structural, microstructural, and dielectric properties—key attributes for next-generation microelectronic applications. High-resolution X-ray diffraction confirmed a rare single-phase cubic structure (space group P2₁3), a significant finding given the structural complexity of mixed-cation tungstates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy revealed a highly uniform microstructure with an average grain size of 8.16 µm and stoichiometric elemental composition, ensuring reliable bulk properties. Impedance spectroscopy provided critical insights, displaying Nyquist plots with two distinct depressed semicircles that delineate grain and grain-boundary contributions, hallmarking non-Debye relaxation behavior. These were precisely modeled using the equivalent circuit (R_1‖CPE₁) + (R_2‖CPE₂), unveiling thermally activated charge transport: resistances decreased with rising temperature, accompanied by intensified interfacial polarization. A synergistic impedance-modulus analysis revealed a pivotal transition from localized to long-range conduction, a cornerstone for understanding ion dynamics in such materials. AC conductivity and dielectric loss data, rigorously analyzed through the correlated barrier hopping (CBH) model, unequivocally confirmed a hopping-dominated transport mechanism—offering new mechanistic depth to tungstate-based dielectrics. Notably, Rb₂Mg₂(WO₄)₃ exhibits exceptionally high permittivity alongside ultra-low dielectric loss, positioning it as a standout candidate for high-performance capacitors, microwave devices, and advanced microelectronics. This work not only advances the fundamental understanding of charge transport in complex tungstates but also paves the way for their practical deployment in energy-efficient technologies.