Production and spectral properties of lattice defects in natural fibrous gypsum colored electrolytically at near room temperature using a pointed anode.

Abstract Natural fibrous gypsum is colored electrolytically at near room temperatures and under various voltages using a pointed anode and a flat cathode. The SO 4 - , SO 3 - , SO 2 - and O − lattice defects are produced in the colored natural fibrous gypsum. No visible characteristic absorption band in the ultraviolet and visible wavelength regions is observed in the optical absorption spectrum of the natural fibrous gypsum before the electrolytic coloration. The characteristic absorption bands of the SO 4 - , SO 3 - , SO 2 - and O − lattice defects are observed in the optical absorption spectra of the colored natural fibrous gypsum. The production of the lattice defects is explained. Current–time curve for the electrolytic coloration of the natural fibrous gypsum and its relationship with the electrolytic coloration processes are given.