Growth and characterization of ammonium nickel-copper sulfate hexahydrate: A new crystal of Tutton's salt family for the application in solar-blind technology

We have obtained the mixed crystals ammonium nickel-copper sulfate hexahydrate compounds which exhibits 98% transmittance in the ultraviolet region, a promising material for UV light filters and UV sensors for solar-blind technology. These crystals belong to the family of Tutton's salt having empirical formula (NH4)2NixCu(1-x) (SO4)2.6H2O and they were synthesized by employing growth from the slow evaporation of aqueous solution technique. The crystallographic parameters, three-dimensional Hirshfeld surface analysis and the calculation of two-dimensional fingerprint plots of the sample crystal (NH4)2Cu(SO4)2.6H2O were determined with the help of single crystal X-Ray diffraction. The X-ray powder diffraction of the pulverized samples were carried out at ambient temperature, 200 °C and 350 °C with the purpose to observe the change in the crystalline structure when subjected to higher temperatures. The thermal analysis of the samples was conducted in the temperature range 30-900 °C with the help of thermogravimetric analysis (TGA), which provides the information about the thermal stability and decomposition process during the heat treatment. Some of our sample crystals demonstrated high dehydration temperature up to 108 °C and they can be considered as an excellent candidate for UV light filters for high temperature applications. The direct and indirect band gaps of the samples were determined from UV-Vis spectra with the help of Tauc's equation. The overtones and combinations of fundamental vibrations of the functional groups our sample crystals were investigated by utilizing near-infrared spectroscopy in the wavelength range 830-2500 nm.