An investigation of structural, thermal, and electrical conductivity properties for understanding transport mechanisms of CuWO4 and α-CuMoO4 compounds

Abstract

Recently, inorganic oxide components with high ionic conductivity have been widely explored due to their high stability, safety, and energy density properties. In this context, the present work focuses on the inorganic oxides CuMO₄ (M = W, Mo), which have been successfully synthesized using the traditional solid-state method. They were characterized by X-ray powder diffraction, thermal analysis, and complex impedance spectroscopy. X-ray diffraction data refined via the Rietveld method indicated that these compounds are well crystallized in the triclinic system with the P space group. Besides, the electrical conductivity behavior of these materials was analyzed using the impedance spectroscopy technique in the frequency range of 10⁰ to 10⁶ Hz and in the temperature range of 443 K to 563 K. The absence of a phase transition observed in the calorimetric study was confirmed by the σ_g and ω_h variations as a function of temperature. The AC conductivity was analyzed by Jonscher's power law. The outcomes of the study on charge transportation in CuMO₄ (where M = W, Mo) suggest that the overlapping large polaron tunneling (OLPT) mechanism was present in CuMoO₄, while the correlated barrier hopping (CBH) and the non-overlapping small polaron tunneling (NSPT) were present in CuWO₄. A correlation between the crystal structure and the ionic conductivity was established and discussed. For the two title compounds, modulus analysis revealed that the charge carriers were mobile over short and long distances at low and high frequencies, respectively. The temperature variation of the M′′ peak showed a thermally activated relaxation process.