Optical and electrical properties of Li₂WO₄ compound

ABSTRACT

The preparation of the Li₂WO₄ compound was made by the solid–solid method under well-defined conditions of temperature, which has not been dealt with in the bibliography. The previous works have been focused on studying the structure and the conductivity of Li₂WO₄ compound, while our work aims to investigate this compound by X-ray diffractometer, DSC, SEM, impedance spectroscopy, and conductivity analysis. Moreover, the optical properties are also investigated. These measures allow us to confirm that the studied sample crystallizes in the monoclinic structure with the space group (P2/m) and the lattice parameters: a = 7.49 Å b = 8.31 Å, c = 5.92 Å, α=γ=90° and β = 96.81°. Li₂WO₄ compound presents a compact structure, wherein the presence of some porosity is noticed. The band gap and the Urbagh energies were determined from the optical measurement. The DSC study shows the presence of an endothermic peak at T = 500 K, indicating the existence of a phase transition. With regards to the electrical properties, the grain and the grain boundary response was modeled by a series combination of two cells, each one of them is composed of a parallel combination of resistance (R) and constant phase element (CPE). The AC conductivity was carried out for a specific range of temperature and frequency, thus allowing the identification of the conductivity mechanism. For the same conditions, the electrical modulus was studied. The theoretical data help us to extract some remarkable results and to confirm the phase transition at T = 500 K.

KEYWORDS:

• MES
• DSC
• impedance spectroscopy
• equivalent circuit
• conductivity

Disclosure statement

No potential conflict of interest was reported by the authors.