Springer Online Journal Archives 1860-2000
Abstract Air-grown KC1 crystals (undoped or doped with KOH) contain two types of OH− impurities: a) a free OH− ion, probably in a substitutional position, b) a reaction product involving divalent impurities like Ca++. The free ion absorbs in two wellknown bands in the ultraviolet (204 mμ) and infrared region (2·8 μ). From concentration measurements by titration of KOH doped crystals, both bands are found to be very weak, the u.v. band having an oscillator strength off=0·13, the infrared band showing 1·2% of the absorption expected from oscillators with appropriate mass and unit dipole charge. In the same crystals, strong carbonate bands (7 μ) are observed; the corresponding CO3 −- concentration, however, is low (less than 3% of the OH− present), according to measurements on samples with known CO3 −- content. — Investigations of the ionic conductivity of KOH doped crystals give evidence of a reaction in the crystal between OH− and Ca++ impurities, as the product of this reaction 1. shows no u.v. absorption, but an OH infrared absorption; and 2. strongly suppresses the extrinsic conductivity to be expected from the Ca++ ions present in the crystal. The consequences of this reaction for conductivity measurements on air-grown KCl without any doping to the melt are demonstrated and the results discussed.
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