title: Electrolytic coloration below 100°C and spectral properties of potassium alum crystals.
abstract: Potassium alum crystals are colored electrolytically below 100°C and under various voltages using a pointed cathode and a flat anode. SO3(-), SO2(-), O3(-), O2(-), O(-) hole-trapped centers and O(0), O(2-), H(+) radicals are produced in colored potassium alum crystals. No obvious characteristic absorption band in ultraviolet and visible wavelength regions is observed in absorption spectrum of uncolored potassium alum crystal. Characteristic absorption bands of SO3(-), SO2(-) and O3(-) hole-trapped centers are observed in the absorption spectra of the colored potassium alum crystals. The hole-trapped centers and radicals come from electric- and thermal-induced decomposition of SO4(2-) radicals and crystalline water molecules. Current-time curve for electrolytic coloration of potassium alum crystal is given. Electron exchanges from electrons and small charged radicals to electrodes induce complete current.
authors.affiliation: Department of Physics, Tianjin University, Tianjin 300072, PR China. Electronic address: jthgu@163.com.
authors.forename: Hongen
authors.initials: H
authors.lastname: Gu
authors.affiliation: Department of Physics, Tianjin University, Tianjin 300072, PR China.
authors.forename: Yutong
authors.initials: Y
authors.lastname: Li
mesh_terms: D000534:Alum Compounds / Q000737:chemistry*; D003116:Color; D003460:Crystallization; D004572:Electrolysis; D013696:Temperature; D013997:Time Factors
chemical_list: D000534:Alum Compounds; C041524:aluminum sulfate
keywords: Defect center; Electrolytic coloration; Low temperature; Potassium alum crystal