Electrolytic coloration and spectral properties of natural fluorite crystals containing oxygen impurities

Natural fluorite crystals containing oxygen impurities are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages. F and F2 color centers are produced in colored fluorite crystals. O2−–Va+, O2−–Va+ aggregate, Yb2+, Ce3+ and Sm2+ absorption bands are observed in absorption spectra of uncolored fluorite crystals. O2−–Va+, O2−–Va+ aggregate, Yb2+, Ce3+, Sm2+, F, M (F2) absorption bands and group of four absorption bands are observed simultaneously in absorption spectra of colored fluorite crystals. Current−time curve for electrolytic coloration of natural fluorite crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained.

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► We expanded the traditional electrolysis method.
► Natural fluorite crystals containing oxygen impurities are colored electrolytically for the first time.
► Useful F and F2 color centers were produced in colored fluorite crystals.
► V-type color centers were produced directly and F as well as F2 color centers indirectly.