Structure and optical properties of Ni1−xCoxWO4 solid solutions

•Complete solid solutions of Ni1−xCoxWO4 have been successfully prepared.•Structure, compositions, and optical properties of the series have been studied.•Gaussian fittings of UV–vis spectra is used to investigate the optical properties.•Ni d–d and Co–W transition contribute to the shift of optical band gap in the series

Ni1−xCoxWO4, x=0–1, polycrystalline samples were prepared by solid state synthesis. Structure, composition, and optical properties of the samples were characterized. The results show that Ni1−xCoxWO4 adopt wolframite structure in all compositions. Cell parameters of the samples systematically increase with Co content. While Co content does not have much effects on FT-IR spectra, it does indirectly change band gap energy of the compounds in the series. Gaussian fitting of diffuse reflectance spectra show that both Ni d–d transition and Co–W metal to metal charge transfer contribute to the shift of optical band gap of the samples.