Growth and characterization of potassium cobalt nickel sulfate hexahydrate crystals: A new UV light filter

Samples of the empirical formula K2+Nix2+Co1−x2+SO42⋅6H2O were grown with a partial occupation of the cations Co and Ni. Mixed crystals with good optical quality were obtained by the slow evaporation growth method. In the decomposition process, these crystals suffer a mass loss of approximately 24%, equivalent to water molecules forming octahedral coordination ions of Ni and Co. The optical characteristics of the grown crystals were measured where transmittance reached more than 80% in the wavelength range of 190-390 nm. By Raman spectroscopy, the vibrational modes of SO42−, H2O and of the octahedral Ni(H2O)6 and Co(H2O)6 were identified.