Disentangling the structure, optical properties, and photoluminescence emissions of NiW1−xMoxO4 (x = 25, 50, and 75%) solid solutions: experimental and DFT studies

Abstract

Solid solutions, formed by combining two transition metal oxides with distinct properties, offer promising potential for optimizing functional characteristics that may be lacking in the parent materials. In this study, NiWO₄ and NiMoO₄ semiconductors and homogeneous NiW_1−xMo_xO₄ (x = 25, 50, and 75%) solid solutions were successfully synthesized via a co-precipitation method followed by heat treatment, without any surfactants or toxic solvents. Using a combination of characterization techniques—including X-ray diffraction, Raman and infrared spectroscopy, X-ray fluorescence, diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy—alongside density functional theory calculations, we elucidate the relationship between the structure, electronic properties, and PL emissions at the atomic level. Furthermore, we propose a relay mechanism in the conduction band, where an electron transport ladder through the Ni–O–W/Mo framework acts as a driving force to modulate PL emissions.