Effect of lithium doping on the structural, conduction mechanism and dielectric property of MnNbO4.

Abstract

The development of multifunctional materials is an exceptional research area, which is aimed at enhancing the versatility of materials according to their wide fields of application. Special interest was devoted here to lithium (Li)-doped orthoniobate ANbO4 (A = Mn), in particular, the new material Li0.08Mn0.92NbO4. This compound was successfully synthesized by a solid-state method and characterized using various techniques, including X-ray diffraction (XRD), which confirmed the successful formation of an ABO4 oxide with an orthorhombic structure and the Pmmm space group. The morphology and elemental composition were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The vibrational study (Raman) at room temperature confirmed the existence of the NbO4 functional group. The effects of frequency and temperature on the electrical and dielectric properties were studied using impedance spectroscopy. In addition, the diminishing of the radius of semicircular arcs in the Nyquist plots (-Z'' vs. Z') showed the semiconductor behavior of the material. The electrical conductivity followed Jonscher's power law and the conduction mechanisms were identified. The electrical investigations showed the dominant transport mechanisms in the different frequency and temperature ranges, proposing the correlated barrier hopping (CBH) model in the ferroelectric phase and the paraelectric phase. The temperature dependence in the dielectric study revealed the relaxor ferroelectric nature of Li0.08Mn0.92NbO4, which correlated the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes. The results demonstrate that Li-doped Li0.08Mn0.92NbO4 could be used both in dielectric and electrical applications.