Structure, optical properties, and magnetism of Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1) solid solution

Graphical abstract: The crystal structure modulation and continuous tenability in band gap were achieved in the Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1) full range solid solution. - Highlights: • A novel Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1) solid solution was synthesized by a two-step method. • They all present a single-phase in the wolframite structure with space group P2/c. • The continuous tenability in band gap was achieved in Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1). • NiWO₄ and Zn_0.5Ni_0.5WO₄ exhibit paramagnetic behavior and obey the Curie–Weiss law. - Abstract: A novel Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1) solid solution with full compositions range has been successfully developed by a hydrothermal–annealing method for the first time. The crystal structure was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra and scanning electron microscopy (SEM). It was found that the entire range of compositions display a single-phase in the wolframite structure with a symmetry P2/c. The diffuse reflection spectroscopy (DRS) measurements on Zn_1−xNi_xWO₄ (0 ⩽ x ⩽ 1) indicated that the optical band gap size across the solid solution exhibits red-shifts from 2.8 eV to 1.63 eV for indirect transition and 3.56 eV to 2.77 eV for direct transition with the increase of Ni²⁺ content. As deduced from the magnetic susceptibility measurements on NiWO₄ and Zn_0.5Ni_0.5WO₄, they are paramagnetic and obey the Curie–Weiss law. Moreover, their effective magnetic moments are determined to be 9.96μ_B and 6.45μ_B, respectively