Crystal Research and Technology
Cryst. Res. Technol. 36 (2001) 147 - Abstract -

A. A. Nechitailov, M. V. Krasinkova, E. V. Mokrushina, A. A. Petrov, N. F. Kartenko, V. V. Prokofiev*

A. F. Ioffe Physical-Technical Institute, RAS, St.-Petersburg, Russia
*Department of Physics, University of Joensuu, Joensuu, Finland

Correlation Between the Impurity Content, the Average Charge State of Chromium Cations and Optical Absorption in Sillenite Crystals Doped by Chromium in Wide Range of Concentrations

Single crystals of sillenites (Bi12SiO20, Bi12TiO20) doped with chromium in a wide range of concentrations from 1 x 10-5 up to 1.8 x 10-2 wt. % were grown by the Czochralski and top-seed solution growth (TSSG) techniques. To estimate the content and the average charge state of chromium in the grown crystals the chemical analysis by the modified diphenylcarbazide method was applied. The dependencies of the chromium distribution coefficient, the average charge state of Cr cations, and optical absorption on the Cr concentration were found. Both the shift of the absorption edge toward lower frequencies and the appearance of an additional absorption band in the near IR were observed when the chromium concentration in the crystals was increased. The experimental data suggest that chromium has at least two charge states and occupies probably different positions in the sillenite unit cell.

Keywords: photorefractive materials, Bi12SiO20, Bi12TiO20, doping, distribution coefficient, absorption


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