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

Abstract Samples of the empirical formula K 2 + N i x 2 + C o 1 − x 2 + S O 4 2 ⋅ 6 H 2 O 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 SO 4 2 − , H 2 O and of the octahedral Ni(H 2 O) 6 and Co(H 2 O) 6 were identified.